Edge case mechanical point: if you send a soldier on a Covert Op with an Ambush Risk, then upgrade gear types they're equipped with while they're out, and then the Ambush triggers, they will still have the pre-upgrade version of the gear in the mission. That is, if you send a Sharpshooter on a Covert Op, then upgrade to Mag Pistols, an Ambush triggering will have them still fighting with a Conventional Pistol. This makes realistic sense, but I'm honestly pleasantly surprised the devs accounted for this!
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All that out of the way, it's time for the actual Covert Ops, starting with the one you normally have to get out of the way on two-thirds of the factions.


Locate (faction)
Contacts (faction), allowing you to perform Covert Operations for them (Starting with 2 per month aside hunting the Chosen), unlocking two Resistance Orders from them, and also recruits one of their soldiers.
Takes 168-240 hours (7-10 days) by default, 288-360 (12-15 days) on Legend.
This only ever presents the Injured Risk.
This Covert Op is unique, in that one faction will be considered 'distant'. The 'closer' one will have no rank requirements in the first slot, while the more 'distant' one will require a Sergeant in the first slot. Every other Covert Op in the game either never demands a minimum rank requirement on the first slot, or always has such a demand. The primary implication of this is that a given run is biased heavily toward a specific order of contact -that you'll have your starting faction, then an easy faction you can make contact with right away, and then another faction you'll have to wait a little to get to.
How relevant this is depends heavily on difficulty. On lower difficulties, you may not even notice the rank requirement by virtue of having multiple soldiers there before you get around to being interested in contacting that particular faction. On higher difficulties, soldiers level slower, and you're liable to actually care, with Legend in particular slowing leveling so much that even with Covert Ops and construction having also been slowed down you'll still probably have a fairly noticeable delay before you can contact the 'distant' faction. As such, on lower difficulties it's not terribly important which faction you start in contact with; you'll rapidly be in contact with the other two if you care. On higher difficulties, you better use Advanced Options to actually force yourself to start with whoever you care about starting with, assuming you do care.
Note that if you have Lost and Abandoned turn on, the Templar will always be the 'distant' faction.
Something else to keep in mind is that your ability to upgrade the Resistance Ring is tied to these Covert Ops. If you're only in contact with your initial faction, you can't upgrade the Resistance Ring. Once you've contacted a second faction, you can upgrade it once. Then you can upgrade it again after you've contacted the third faction. This usually isn't important, as Avenger Power is limited and you should always endeavor to build Power Relays on Exposed Power Coils, which are always in the bottom two rows of the Avenger so it takes a while to generate enough Power to make sense to upgrade the Resistance Ring... but it is possible to get free Power from an early Rumor, or for the Templar to offer one of the Hidden Reserves Resistance Orders early. Depending on what Resistance Orders you've rolled, that may make an early Resistance Ring upgrade very appealing, and if you've been slacking on the Locates you might find you can't get the upgrade before the month rolls over. Oops.
This should happen only rarely, in part because the Locates are very high-value; a free soldier, a pair of Resistance Orders, and more Covert Op options so you're more likely to have what you want available. Very few Covert Ops can compete with that value; pulling an Engineer with Tech Support is one of the only Covert Ops I'll prioritize over Locating a faction.
Technically, Locate Faction isn't part of the following chain, but it effectively is, so...


Behind Enemy Lines
Provides 2 more Covert Operations per month for the faction, unlocks one more random Resistance order, and opens up one Resistance Order slot for the faction.
First slot always demands the soldier be at least Sergeant.
Takes 168 hours (7 days) by default, 336 (14 days) on Legend.
Note that access to this is tied to whether you've got the ability to encounter a given Chosen in the first place. That is, if you're in contact with only two regions, and they're both controlled by the Hunter, you won't be able to perform Behind Enemy Lines for the Assassin or Warlock. This is usually not a big deal, but occasionally you'll manage to contact literally half the world without having run into your third Chosen, and so still be unable to build Influence with one of your Resistance factions.
Also note that increasing Influence with a Resistance faction will add additional Covert Ops to the monthly rotation, permanently. If you don't like any of the Covert Ops on offer, you should try to build Influence to add more options. As you can't mess with Resistance Orders except at month-to-month transitions, it's better to arrange for an Influence-raising Covert Op to finish before the month rolls over, rather than after; if you can, you should ideally perform them earlier in a month than other Covert Ops.
Each faction will offer exactly one of these missions, and will do so every month without fail once you've made contact with the relevant Chosen, with this not counting against their per-month Covert Op limit. (This being the secondary caveat for mid-month Covert Op acquisition: Behind Enemy Lines is added immediately after you're in contact with the relevant Chosen) Which faction hunts which Chosen is random per run, and is tied together with the Chosen Weakness system: whichever Chosen is weak to Reapers will have their Behind Enemy Lines attached to Reaper Covert Ops, whichever Chosen is weak to Templar will have their Behind Enemy Lines attached to Templar Covert Ops, etc. You also obviously have to have completed the faction's respective Locate Faction Covert Op, though realistically most players probably make contact with all the Resistance factions before it has a chance to be relevant -for one thing, the game always ensures that the Resistance faction you start out in contact with is the Weakness of whichever Chosen is in control of your starting region, ensuring you'll have access to their Behind Enemy Lines immediately after the first mission you encounter a Chosen at all.
Also notice that Legend difficulty flat-out doubles the time Behind Enemy Lines takes. This applies to all the Covert Ops that are for hunting the Chosen and by extension building Influence with a Resistance faction, where for other Covert Ops it's roughly a 50% increase in duration; this means that on Legend difficulty it takes a lot longer and is much more burdensome to get into position to assault a Chosen Stronghold, especially since you already fit fewer Covert Ops into a month. On lower difficulties, you may clean out all the Covert Ops you actually find high-value and then end up sending a team Chosen-hunting for lack of a better thing to do. On Legend, you're almost certainly sacrificing access to things you actually cared about -if nothing else, it's slowing down your Covert Op stat-grinding.
Something else to note is that the Chosen hunting chain of Covert Ops actually randomizes each month, changing up its Risk distribution, changing whatever bonus is being offered in one of the slots, and potentially changing whether a third slot exists or not, as well as what said third slot's parameters are. If a given Chosen hunting Covert Op has every Risk at the highest rating and you don't want to risk that, you can put it off a month and hope it's less dangerous next month.
Completing Behind Enemy Lines always immediately replaces it with...


Find the Stronghold
Provides 2 more Covert Operations per month for the faction, unlocks one more random Resistance order, and opens up one Resistance Order slot for the faction.
First slot always demands the soldier be at least Lieutenant.
Takes 240 hours (10 days) by default, 480 (20 days) on Legend.
Like Behind Enemy Lines, this is perpetually on offer once unlocked, and also like Behind Enemy Lines will nonetheless re-randomize its parameters each month.
This also has the consequence of causing the Chosen's Stronghold to become visible on the Geoscape, but this doesn't matter; unlike plot missions like the Blacksite, it's not necessary to make contact with the region containing a Chosen's Stronghold, and there's no alternate mechanic to make it strongly relevant. The Avenger will have to travel to it when you hit it, so the exact location technically matters, but this is an extremely minor thing, and it doesn't matter at all at this step.
Below Legend difficulty, the rank requirement is rarely a burden unless you're really careless with soldier lives or are bizarrely aggressive about spreading experience evenly. Often you'll already have a Lieutenant before you even want to perform Find the Stronghold; for one thing, all of Find the Stronghold's benefits are replicated by Behind Enemy Lines, while taking less time to perform. Thanks to the wildcard slots, and the inability to predict what Resistance Orders you'll get, it's usually better to perform Behind Enemy Lines on the other two Chosen before you get around to Find the Stronghold on any Chosen.
If this were the final step, you might occasionally be frustrated by your inability to beeline to attacking the Chosen, but it isn't, and the next rank requirement is far more relevant no matter your difficulty. As such, you really should usually just perform Behind Enemy Lines on everyone first. You'd basically need a bizarrely long streak of only making contact with regions your initial Chosen controls for this to not be true, and this is very unlikely, maybe even impossible.
On Legend, getting to Lieutenant is actually fairly slow, and you may find yourself wanting to Find a Stronghold, but unable to, or only able to do so with a soldier you don't want to spare for so long. In conjunction with how much slower you are to contact new regions on Legend, it's entirely possible to have only met two Chosen and be struggling to unlock Resistance Orders and Resistance Order slots, in part because the Blacksite's region is always controlled by the Chosen that controls your starting region, and the game always arranges it so there's exactly two regions you can contact right away, one of which is the Blacksite; in conjunction with your initial Contact limit being 3, it's actually pretty unlikely you'll meet all three Chosen particularly early. You'd basically have to deliberately avoid the Blacksite and then get lucky with your third Contact being the third Chosen, or get extra Contacts early from a Rumor or from one of the Resistance Rising Resistance Orders... and you'd still need to get lucky.
Completing Find the Stronghold immediately replaces it with...


Into the Fire
Unlocks the ability to assault that particular Chosen's Stronghold and provides 1 more Covert Op per month.
First slot always demands the soldier be at least Major.
Takes 288 hours (12 days) by default, 576 (24 days) on Legend.
Into the Fire is the last Op of this chain, with no further Op unlocked. I've not personally tested it, but I'm pretty sure that if you aborted or failed a Chosen Stronghold assault that the respective Into the Fire would re-activate, going by in-game dialogue.
As usual, once unlocked it perpetually sits in the pool, separate from the monthly limit, though still re-randomizing bonuses and so on each time the month changes.
In any event, you do this for one of two reasons; either you want to finish off the Chosen in the near future, or no regular Covert Op is particularly appealing so you might as well get a Find the Stronghold out of the way right now. Yeah, it adds another Covert Op per month, but... so? You already have 6 per month before doing this, and you'd get two more out of doing some other Behind Enemy Lines or Find the Stronghold, and it would be faster and provide more Resistance Orders and a Resistance Order slot.
The Major requirement is also very demanding. On Veteran it's not so bad; if you focus on getting all the Resistance Order benefits and so on, you may have a Major notably before you bother to perform an Into the Fire. On Commander, you're basically guaranteed to be forced to wait a bit unless you ram through rank ups on one soldier via Covert Op promotion rewards. On Legend, even that is still likely to involve a delay!
This ensures you can't beeline to a Chosen and do something silly like update your Rangers to better-than-tier-3 weaponry before you've even unlocked magnetics. This is good design!
Also notice that on Legend this basically eats an entire month if you have the Resistance Ring unmanned. Even manned, that's 16 days; more than half of any given month. This can make it hard to fit in if you're desperately scrambling to cram in other Covert Ops, like Sabotage, further contributing to how long it takes to actually get to hitting the Chosen.
Especially since the Chosen Stronghold assault is basically guaranteed to leave your entire squad Tired-to-Shaken, making the assault difficult to fit into your mission schedule. They're hard missions, too; ideally you're sending your best soldiers, making it even costlier to have them taken out of action.
This is actually one way SPARKs can shine in War of the Chosen; their inability to get Tired means they grow in rank quickly, so often they're among your best soldiers for a good chunk of the game and sending them into a Stronghold doesn't inherently take them out of action for days. A couple of SPARKs can make it a lot easier to fit Stronghold assaults into your schedule. It's one of the many little ways War of the Chosen makes balance and design better in spite of minimal direct alteration to existing tools, which is one of its most impressive qualities. Especially given it was clearly rushed!
Teamwork Training
The two sent soldiers will, once returned, have enough Bond experience to reach the next Bond level.
Takes 120 to 168 hours (5-7 days) by default, 192-288 (8-12 days) on Legend.
Note that you'll still need to actually make the Bond happen, including using the Training Center for Bond Levels 2 and 3.
This only ever presents the Injured Risk.
This is primarily useful if you have a particular Bond pair you want to happen, where their Compatibility is inconveniently low. You can ram through a level 3 Bond by sending them on Teamwork Training, Bonding, rinse and repeat.
I don't really consider any Bondmate class combos to be so outstanding as to be worth the bother, and usually only go for Teamwork Training as either filler when no other Covert Op is particularly appealing, or if it's the only thing offering a bonus I want. (eg I'm trying to get a Major already so I can do Into the Fire) And on Legend only the latter is liable to crop up, since I can't burn through all the good Covert Ops so consistently.
That said, occasionally I'll have a soldier hit a high level without getting a natural high Compatibility Bond going, and bother to ram a Bond through because eg I'm definitely bringing a Reaper into the final mission and would prefer they have a Bondmate.
So this is merely a bit niche, not useless. Niche is perfectly okay design.
Combat Preparedness
Adds a partially randomized number of Ability Points to the XCOM pool. (You will be told the exact amount provided by a given Covert Op ahead of time)
Takes 168-240 hours (7-10 days) by default, 288-360 (12-15 days) on Legend.
I haven't sat down and marked out every single case, nor found a file explicitly laying out the possibilities, but this is always in the 10-20 sort of range. (I think 19 is the highest I've seen, but don't quote me on that)
Combat Preparedness is kind of a default fallback Covert Op if you're not grabbed by anything in specific. Worst comes to worst, whatever team takes on the final mission will appreciate a sudden injection of Ability Points; unless you've been obsessively focusing on maximizing Ability Points, or field nothing but SPARKs into the final mission, it's extremely unlikely you'll run out of skills to buy.
Combat Preparedness is actually pretty good, but I tend to end up prioritizing other things because if you don't immediately turn around and spend the AP you're not benefiting from it at all, and even if you do immediately spend it on a soldier it's a 'local' benefit; boosting one soldier helps when they go on a mission, but you can't bring a given soldier into every mission in War of the Chosen. (Except SPARKs, but they don't benefit from AP so they're irrelevant to this point) It's usually going to be more useful to prioritize Covert Ops that have wider benefits.
Of course, if there's no such options, it's a very solid fallback Covert Op, as I already said. Don't write it off.
Tactical Education
Permanently upgrades by one tier the Combat Intelligence of the soldier placed in the first (upper-left) slot of this Covert Op. The effect is retroactive, adding whatever Ability Points they should've gained by their current rank with their new Combat Intelligence to their personal pool. Resistance soldiers are ineligible for this benefit, and cannot be placed in the first slot.
Takes 120 to 168 hours (5-7 days) by default, 192-288 (8-12 days) on Legend.
Basically, if you have Geniuses (Who aren't Resistance soldiers), turn them into Savants via Tactical Education. That way you don't have to hope for that teeny-tiny chance of just naturally rolling a Savant.
If you don't have any Geniuses, it's still disproportionately useful to send Gifted soldiers to become Geniuses, particularly since you can always send them again so they become Savants. Just... don't bother sending Standard or Above-Average soldiers unless you actually can't do better.
For reference, part of why I say converting Geniuses to Savants is worth it and am more dubious on it below that point is how this compares to Combat Preparedness providing a value in the teens. Jumping from a Genius to a Savant is a lifetime gain of 18 Ability Points, comparable to the upper ranges of Combat Preparedness. Jumping from Gifted to Genius is a lifetime gain of 12 Ability Points, comparable to the lower end of Combat Preparedness' payoff. Raising the lower two tiers of Combat Intelligence is a lifetime gain of... 6 Ability Points, well below what Combat Preparedness gives. As such, if you really want more Ability Points on a soldier with a low CI, it's better to do a Combat Preparedness Covert Op on the idea of spending XCOM Ability Points on them. Raising their own Combat Intelligence is only advantageous if you're worried about the possibility of retraining them -and frankly, while you can retrain people in War of the Chosen, there's not much reason to. Why redistribute when you can keep what you have and buy what you want? Especially since retraining takes a soldier out of action for several days, while buying skills is instant.
The main argument in Tactical Education's favor over Combat Preparedness is that it's notably faster. And that's a little misleading, since you can never leverage Covert Operators with Tactical Education; Tactical Education rolling high on its duration while Combat Preparedness rolls low on its duration will result in them being equal, and then you can send a Bond pair on the Combat Preparedness Covert Op so it's suddenly the faster option. And it's not like Tactical Education is even, on average, twice as fast as Combat Preparedness, which is the kind of range it would need to be to make up for how much less AP it provides for an Average or Above-Average soldier. You should still consider using Tactical Education to eg slip an extra Covert Op into a month before kicking off a longer one that'll complete in the next month, but for Average and Above-Average soldiers that's about it.
Tactical Education is one of the safer Covert Ops, never having a Risk other than Injured. (Before Dark Events...) It also is always exactly one soldier slot, with a guaranteed optional slot for removing the Injured Risk by using a Scientist in specific, which is unique behavior. (And the reason why you can't leverage Covert Operators with it)
Helping Hand
Permanently raises X-COM's Supply income by a partially randomized amount, ranging between 15 and 25. (You will be told the exact amount provided by a given Covert Op ahead of time)
Takes 120 to 168 hours (5-7 days) by default, 192-288 (8-12 days) on Legend.
This is inexplicably one of the more dangerous Covert Operation types, fairly prone to carrying all three Risks at high ranges. I mean, yeah, it'll add up, but a successful run doesn't have that many months in it. Maybe a whole year. So... gain 15 Supplies, twelve times, maybe? That's not even 200 Supplies added. The game would need to have a lot more length to it for this to make sense as having so many Risks.
I never bother unless something odd is going on like I desperately want to promote someone and Helping Hand is my only option for doing so. It's that bad.
A specific region will be cited for having its income raised, but as far as I'm aware this doesn't matter. The game is perfectly happy to say some region you aren't in contact got the boost, and you'll still get the extra Supplies when the month rolls around. I suspect if the game had gotten more polish the region claimed would've been made to matter, but as-is I'm pretty sure it's irrelevant flavor.
Possibly the most poorly-designed Covert Op, honestly.
Signal Boost
Permanently raises X-COM's maximum regional Contact limit by 1.
Takes 120 to 168 hours (5-7 days) by default, 192-288 (8-12 days) on Legend.
One of the most valuable and helpful Covert Ops to get, particularly early in the game when it's difficult to justify setting aside a facility block and Supplies for increasing your Contact limit via facility construction. Even once you have more than enough Contacts, this can be a de-facto free Engineer recruitment, if it lets you shuffle an Engineer out of a Resistance Comms facility slot. Recruiting an Engineer via Covert Op takes roughly twice as long as Signal Boost, too!
I personally consider Signal Boost to be the single most helpful Covert Op in the entire game, or at worst second to Sabotage. It saves Supplies, lets you earn more Supplies faster, lets you unlock Continent Bonuses sooner, make contact with the other Chosen faster to unlock their respective Chosen hunting chains to raise Influence, potentially lets you hit an Avatar Project Facility sooner to stave off the doom clock, makes it more acceptable to prioritize facilities that aren't Resistance Comms, its benefits are not readily replicated some other way... the only downside is that it tends to be a Risky Covert Op, and frankly that's not much of an issue, not compared to its tremendous benefits.
I basically always try to prioritize Signal Boost if I'm not at the point of 16+ Contacts already. It's just that good.
Supply Run
Provides a partially-randomized amount of Supplies to X-COM. (You will be told the exact amount provided by a given Covert Op ahead of time) The potential amount provided goes up a little with each month that passes.
Takes 120 to 168 hours (5-7 days) by default, 192-288 (8-12 days) on Legend.
Supply Run is almost flatly better than Helping Hand. It starts out generally providing around 80-100 Supplies (And slowly goes up as your run progresses, to boot), where Helping Hand is an income increase of 15-25, meaning it will take more than 4-7 months for Helping Hand to break even with Supply Run! At its initial numbers, when Supply Run gets better over time and Helping Hand de-facto gets worse over time! (Because if you're 2 months from beating the game, Helping Hand is only adding 30-50 Supplies) The long haul advantage of Helping Hand doesn't really matter, either: you desperately need Supplies early on, but past the midgame the Supply crunch fades, because you stop building Supply-intensive facilities, stop having GTS upgrades to purchase, meet your needs on Supply-intensive Items like Medikits and Bluescreen Rounds, and make contact with so many regions your Supply intake becomes larger. Your production bottleneck in the mid to late-game is generally Alien Alloys, Elerium Crystals, Elerium Cores for Proving Ground projects, and the limit of one object being made at the Proving Ground at any given moment. In the extreme long haul, you can be sitting on thousands of Supplies with nothing useful to spend them on! This means that it doesn't matter that an early Helping Hand will add up to more Supplies in the long haul: by the time you're far enough along for an early Helping Hand to have pulled ahead of an early Supply Run, you don't care.
Worse, Supply Run is inexplicably safer than Helping Hand, with Helping Hand generally carrying all three Risk types at a modest to high chance where Supply Run is usually just a low Risk of Injury. This means Supply Run can be easily handled by just throwing a couple of Squaddies at it, instead of needing to send more competent soldiers just in case of an Ambush, and also means no possibility of losing a soldier outright to Capture.
I really feel like Helping Hand should've been the safer one. It would've been better for the game design, and it would also have made more logical sense: Helping Hand is apparently sending your soldiers to motivate resistance cells to give a little more, or helping them get more on their feet so they can spare more, whereas Supply Run is actively raiding guarded ADVENT supplies. Shouldn't the one that involves striking into enemy territory be the one that's more dangerous? What, are the resistance cells prone to getting angry and selling out our troops to ADVENT, or something?
Also not helping is that Higher Learning and Tech Support both exist, are often safer than Helping Hand, and are both better long-term investments. Tech Support providing an Engineer is even very directly overlapping with Helping Hand in the early game, due to you getting Supplies out of Excavating the Avenger!
Anyway, Supply Run itself can be very useful in the early to midgame when you are perpetually hungry for Supplies, particularly for timing considerations; maybe you'd really like to hit the Blacksite soon, but want to purchase magnetic weapons first, and don't want to wait for the month to roll over. Supply Run will probably be faster.
Later in the game, Supplies largely stop mattering; focus your efforts elsewhere.
Intel Collection
Provides a partially-randomized amount of Intel to X-COM. (You will be told the exact amount provided by a given Covert Op ahead of time)
Takes 120 to 168 hours (5-7 days) by default, 192-288 (8-12 days) on Legend.
Intel is one of your more important resources. Very early on it's not particularly important, but once you're in the midgame, trying to aggressively contact new regions, your Intel hunger is basically bottomless, even if you never reveal a hidden Dark Event or buy anything from the Black Market, and late in the game it can still be very nice to buy Superior Weapon Attachments or PCSes. Crucially, Intel is your hardest resource to generate 'on-demand'; if you desperately need Supplies, you can sell stuff at the Black Market. If you desperately need Alien Alloys or Elerium Crystals (Or you need more Supplies than selling stuff covers), you can buy them at the Black Market. Intel, meanwhile, is only acquired from specific mission types that occur on a fixed cycle outside your control, hack rewards randomly offering Intel, and by cracking open randomly-looted ADVENT and Alien Data Caches. (Outside Intel Collection itself, of course)
Of these, the only one you can push for is to complete Skullmining as fast as possible, build multiple Skulljacks, and just constantly Skullmine enemies and accept that you're going to get soldiers injured as a result. And meanwhile your main methods of acquiring other resources on-demand spend Intel, so more Intel gives you much greater flexibility down the line.
As Intel Collection also trends toward being a relatively safe Covert Op, generally only having a Injured Risk, it's one of the better Covert Ops to grab if you're not clear something else is a priority. There's basically no such thing as too much Intel; if you've got nothing to spend it on, you probably don't have anything to spend anything on, basically.
Scavenge Alien Loot
Provides 2 Elerium Cores.
Takes 168-240 hours (7-10 days) by default, 288-360 (12-15 days) on Legend.
The in-game description of Scavenge Alien Loot makes it sound like it provides randomized loot (In part because it sounds exactly like the Rumor that does reward random loot), but I've only ever gotten Elerium Cores out of it, having launched it dozens of times. I'm not 100% certain it's always exactly 2 Elerium Cores; it's possible it actually varies and I've just missed the times it wasn't 2 in my own runs. It's an outside possibility, mentioned for completion's sake.
Scavenge Alien Loot is also one of the more dangerous Covert Op types, which makes in-universe sense but tends to mean it's preferable to go for PCSes or Weapon Attachments over more Elerium Cores unless your run is having very bad luck with Elerium Core counts.
This is exacerbated by the fact that Elerium Cores have a substantial diminishing returns aspect. Everything you spend Elerium Cores on is either a one-time project (eg Skullmining, Battlefield Medicine), or something where, without actually abandoning soldier corpses, you only really want a few copies. Once you've got a couple of Venom Rounds, a couple of AP Rounds, and a couple of Dragon Rounds, further Experimental Ammo Projects is something you can do, but the payoff is barely there. That kind of thing.
As such, I actually only rarely bother with Scavenge Alien Loot. Most runs have more than enough Elerium Cores to get everything done; Proving Ground time is usually a much more pertinent limitation than Elerium Core counts.
Still, I have had a few runs that were starved of them, and if you're fond of SPARKs that increases your Elerium Core demand enough you should certainly consider doing Scavenge Alien Loot at least once.
Fabricate PCS
Generates a random PCS of Superior quality.
Takes 168-240 hours (7-10 days) by default, 288-360 (12-15 days) on Legend.
One of the safer Covert Ops, I've only ever seen it carry a chance of injury, and usually a low chance.
I don't tend to prioritize this personally, since most PCS types aren't very useful and so it's just gambling on the possibility of meaningfully helping, but it's pretty rare for a run to have more than enough PCSes for everybody, since they can't be swapped around and you're generally floating 15+ regularly-active soldiers in War of the Chosen. As such, it's one of the better Covert Ops to go for if nothing particularly great stands out.
It's also more worth considering early in the game, where you don't tend to find Superior PCSes at all; Fabricate PCS doesn't make a PCS of a tier appropriate to your current circumstance. It's always a Superior-quality one, even if you're at the beginning of the game where PCSes found as loot or on the Black Market are only occasionally better than Basic. I usually prioritize things like hunting the Chosen, but still, it is worth considering in the early game, as its value is at that point unreplicable and potentially pretty pronounced.
Manufacture Weapon Upgrade
Generates a random Weapon Attachment of Superior quality.
Takes 168-240 hours (7-10 days) by default, 288-360 (12-15 days) on Legend.
Like Fabricate PCS, I've only ever seen an injury chance on this one, and usually at a low chance.
Also like Fabricate PCS, I rarely bother. Gear can be swapped around, so even though a given mission's squad needs more Weapon Attachments to be fully kitted out than PCSes, your overall force will hit maximum value a lot sooner. Weapon Attachment quality is also uneven; getting a Superior Laser Sight out of this is just plain underwhelming. Further, in the long haul you'll largely stop using regular Rifles, Shotguns, and Sniper Rifles, because the Chosen versions are so much better, so your overall Weapon Attachment needs are even less than they first seem. And if you have the Tactical Legacy Pack (Or, to a much lesser extent, Alien Hunters), you'll have even less interest in burning Covert Op time on Weapon Attachments; why manually upgrade a Shotgun when the TLP Shotgun already has the Weapon Attachments that are the overall best fit to a Shotgun anyway? (This particularly exacerbates the Laser Sight issue, since Shotguns are by far the best recipient for a Laser Sight)
As Weapon Attachments on the Black Market tend to be cheap... I personally prefer to prioritize Intel Collection and buy what Superior Weapon Attachments I ultimately want, if the loot RNG proves uncooperative. It's more reliable, and Intel Collection is faster than Manufacture Weapon Upgrade to boot.
I still occasionally perform Manufacture Weapon Upgrade, but always from a combination of factors conspiring together. Maybe in a given month all the things I most want to do have Capture chances, so I go for Manufacture Weapon Upgrade to avoid risking my soldiers while still getting some manner of long-term benefit. That kind of thing. Not because it's a particularly meritful Covert Op.


New Resistance Order
Unlocks a random Resistance Order. Skirmishers will provide a Skirmisher Resistance Order, Templar a Templar one, and Reapers a Reaper one. You will be informed ahead of time which Resistance Order is on offer.
Takes 168-240 hours (7-10 days) by default, 288-360 (12-15 days) on Legend.
This tends to be safe-ish, only rarely combining all three Risk types.
This is one of the most judgment-call-y Covert Op types. Some Resistance Orders are horribly lackluster and almost never worth grabbing, and some are amazing and basically always worth grabbing, but in most cases you'll have to consider a large number of factors when deciding whether a given Resistance Order is worth pursuing; how many of your Resistance Order slots are currently filled with high-value Resistance Orders? Are any of your current Resistance Orders going to stop helping in the near future? Is the Resistance Order on offer one that will have its value close off soon, and if so, can you adjust your plans to get greater value out of it anyway, and if so, do you even want to?
What's your current situation regarding hunting the Chosen? If you're already in contact with all three of them and only performed Behind Enemy Lines on one of them, performing the Chosen-hunting chains will tend to be the smarter choice, opening up an additional slot and adding two Resistance Orders to your options, as well as bringing you closer to finishing off a Chosen for good. But maybe you don't want to risk missing out on this Resistance Order? Better prioritize it anyway, then.
Or maybe it's a Resistance Order that would be really helpful right now, such as that you really need additional contacts ASAP to avoid the Avatar Project killing you, it's Resistance Rising II, and it's going to take too long to get a Resistance Comms facility online, with the next month going to roll around shortly after you've finished the Covert Op. Even though Resistance Rising II is actually low-value on the whole, in that situation you should be going for it even if it's got all the Risks at max.
This is great design and it's by far my favorite Covert Op type from a design perspective.
A minor wrinkle worth pointing out: the game will not offer a Resistance Order via Covert Op if you already have that Resistance Order, but having a Resistance Order sitting in your Covert Op pool won't prevent the game from giving you that exact Resistance Order when raising Influence with the relevant Resistance faction. I'm not sure what happens if you then go for this redundant Resistance Order, but in any event if you're thinking of grabbing a Resistance Order and raising Influence with the same faction in the same month, it's probably better to grab the Resistance Order and then raise Influence, certainly if you will complete both before the month rolls over.
Also keep in mind that Resistance Orders can only be applied at the beginning of the month, and you're not given the Resistance Order until the Covert Op completes. It's thus best to arrange for Covert Op-derived Resistance Orders to be acquired shortly before the end of the month, not after. Pay attention to when your next Supply Drop is listed as occurring, and compare the time to the Covert Op's duration. Even if you'd like an Engineer ASAP, it may be better to grab the Resistance Order first, if whichever is grabbed second will arrive just after the month rolls over and you want the Resistance Order online ASAP.
Higher Learning
Provides an additional Scientist.
Takes 240 to 288 (10-12 days) hours by default, 360-432 (15-18 days) on Legend.
It's mildly interesting to me that it's Tygan being depicted here. Only mildly, but still.
Early in the game, this can be pretty strongly worth considering. An extra Scientist from the beginning of the game will have a pretty dramatic effect on your overall Research cycle, and is a lifetime benefit.
Later in the game, it's rarely worth considering. Scientists have diminishing returns, each one providing less of a proportionate increase than the last; if you have no Scientists, Higher Learning spikes your Research rate by 33%. When you already have several, another Scientist will be something underwhelming like a 9% increase in Research speed. They also don't affect Breakthrough speed at all, and Instant Autopsies bypass the normal Research process entirely, so a non-trivial fraction of your Research doesn't benefit from additional Scientists any. Furthermore, Higher Learning is one of the moderately risky Covert Ops, usually having an Ambush or Capture Risk, sometimes both in addition to the usual Injured Risk.
Definitely consider it if you get it on offer in the first couple of months, but probably ignore it past that.
Tech Support
Provides an additional Engineer.
Takes 240 to 288 hours (10-12 days) by default, 360-432 (15-18 days) on Legend.
This really looks like they put Tygan in a hard hat, took off his glasses, and used lighting to obscure his face, which is... uuuuh? He's even wearing the same coat as in Higher Learning, it just looks different from the monitor's yellow light and the shadows being stronger. I guess it's another casualty of War of the Chosen being rushed?...
In any event, Tech Support should generally be a high priority in the early to midgame. When you're still excavating the Avenger, getting additional Engineers accelerates your intake on Supplies, Alien Alloys, and Elerium Crystals, and also accelerates your construction timetable so you eg get additional Power going faster to then get important structures like the Shadow Chamber up faster. This is a huge set of gains to be getting, and once you're done excavating the Avenger any leftover Engineers are still relevant for boosting Resistance Contacts, improving healing times via the Infirmary, getting a Lab built faster to accelerate research sooner, etc.
Once you're basically done excavating and have the Resistance Ring and Proving Ground continually manned, Tech Support should probably be ignored. Even if it might be nice to have an Engineer accelerating wound recovery times or something, the fact is the game will force you to recruit additional Engineers via VIP Rescue missions, and you may find yourself getting still further Engineers via Guerrilla Ops, such as if a Dark Event you're terrified of will be blocked by a Guerrilla Event offering an Engineer as a reward. You can't sell off excess Engineers, and there's a hard limit on how many Engineers can actually help on the Avenger. So eventually additional Engineers is literally worthless.
As such. when you're close to being done Excavating and have the Proving Grounds and Resistance Ring continually manned, additional Engineers will tend to be a waste of Covert Op time, better spent on other things.


A Hero's Welcome
Provides one Resistance faction soldier, of the appropriate Resistance faction.
Takes 168-240 hours (7-10 days) by default, 288-360 (12-15 days) on Legend.
Yeah, this is literally the Covert Op for contacting a faction, just minus the Resistance Orders and unlocking Covert Op access with the faction.
It's also something you should basically automatically do, as it's a uniquel safe Covert Ops that doesn't necessarily carry any Risk at all, and more soldiers is of course a good thing given the Fatigue mechanic.
Do note that A Hero's Welcome actually has a minimum Influence requirement ("High"), where you can be offered it as a Covert Op but not be allowed to actually perform it unless you raise Influence with the faction first. You may wish to prioritize getting Find The Stronghold out of the way on your starting faction to minimize the odds of this delaying your additional recruit down the line.
Also note that it's actually possible for the game to decide to hold onto A Hero's Welcome from one month and also offer it again in the next month, making it actually possible to recruit three copies of a Resistance soldier if you get lucky/are willing to try to game the system. (Which is one of the best examples of why I'm doubtful this holdover mechanic is intentional)
In any event, you should do this when offered. (Aside maybe the gaming-the-system point) Resistance classes are above-average in quality, Reapers in particular dramatically improve your quality of life to have consistently available, and War of the Chosen's Fatigue system makes it important to have a large number of soldiers, so a free soldier is always welcomed. You don't necessarily need to prioritize it over other stuff, but you shouldn't ignore it indefinitely.
One reason you don't necessarily need to prioritize it is that soldiers acquired from this Covert Op are pre-leveled to keep up with you, rather than starting at Squaddie the way your initial Resistance class soldiers do. So it's not a case of 'get them early so you can get started on leveling them early'. You can get all the way up to a Colonel out of this Covert Op. (Though generally if you're getting a Colonel, it's because you got an existing Resistance soldier killed late in a run...)
A Hero's Welcome itself is only offered under two circumstances; firstly, whatever faction is your starting faction will eventually offer it spontaneously. Secondly, if your Barracks is ever at less than the cap of a given Resistance class type, the appropriate faction can randomly elect to offer A Hero's Welcome until you stop being below the cap. Note that soldiers being on a Covert Op still has them considered to be in the Barracks; you're only considered to not have them if they die, are Captured, or if their class changes for some reason. (This last point will never occur in normal circumstances, but can crop up if you're using certain kinds of mods) Conversely, note that the game doesn't 'count' an ongoing A Hero's Welcome for tallying troop counts: it's possible to start it close to the end of a month, and when it finishes have another waiting because the game still considered you to be under your cap.
Also, this is one of a few examples of the game referring to Resistance soldiers as 'Resistance Heroes'. I've not used that terminology on this site because I feel it's misleading; yes, Resistance soldiers are all above-average in quality, and yes you only get a limited supply of them, but they honestly don't stand out that much in power or otherwise function in a manner that makes the 'hero' terminology feel justified.
A contributing factor in why I don't use this terminology is that I'm pretty sure the development concept changed in a manner that undercut the notion that these soldiers in particular are 'heroes'. There's some evidence the Resistance factions were supposed to be seen in the field in a more substantive manner than we got, such as Bradford having dialogue claiming a Resistance faction has sent some soldiers to meet up with you in mission types where no such thing actually happens, and bits and pieces of how this was handled make me suspect that at some point in development the Resistance factions would've used regular X-COM classes as the core of their forces, with the distinctive Resistance classes we got being uncommon elites in this concept. That is, if the Reapers sent a squad to support you, it would be a gaggle of core class soldiers, with maybe one Reaper-the-class leading the force.
But then in the game we actually got, the Resistance factions are apparently uniform; every Reaper-the-faction is a Reaper-the-class, every Templar-the-faction is a Templar-the-class, etc, and this itself makes it harder to buy any given individual is amazing enough to justify the 'hero' label. In a version of the setting where each faction was, say, a thousand or so individuals, but less than one in ten of those individuals proves able to master the skills necessary to justify the faction class, that would make it believable that the Resistance classes are super-classes yet Resistance factions aren't blatantly crowding out X-COM in importance. With every random ADVENT soldier who goes rogue being a Skirmisher class, though, having them be super-classes would be a strain on the narrative, making it difficult to buy that X-COM is the primary organization getting things done. As-is, the Resistance classes are a bit above-average, but they also seem to be less flexible than X-COM, and so it's intuitive that they excel at certain tasks but couldn't possibly tackle the full range of tasks X-COM has to overcome, especially in conjunction with X-COM's access to the Avenger making it uniquely mobile as an organization.
I kind of doubt these concerns per se were on the collective mind of the developers, but regardless it looks to me like Resistance faction classes were probably originally conceptualized as more stand-out powerful than they ended up being, and the 'hero' terminology never got updated to match this concept shift. So I don't use the terminology myself, because I suspect it's in some sense not true of the final game's intentions.
Personnel Extraction
Completing the Covert Op generates a mission to rescue the captured soldier.
Takes 120 to 168 hours (5-7 days) by default, 192-288 (8-12 days) on Legend.
Note that the actual rescue is a separate mission you can send whoever on (That is; the soldiers sent on the Covert Op aren't forced to be the rescuers), and isn't a Covert Op. Also note that you have to fly the Avenger to the rescue mission site. Further note that the rescue mission only lets you take three soldiers, and that you're really not supposed to kill your way through the map. Which makes it a bit annoying that picking up the captured soldier automatically breaks your squad's Concealment... you can avoid alerting the base by succeeding at the door hacking roll (Assuming you pick the 'no alert' reward), and this also determines the evac situation; fail the roll, and the evac zone generates nearby, out of your control, inconveniently far. Succeed, and you get to designate the evac zone, ensuring your squad can immediately exit the mission once you're ready to pick up the body with no risk. (Though this is buggy, where the game is unreliable about preventing you from designating your own evac zone)
Rescue missions are unusual in that the detection radius on enemies is substantially reduced, aside Turrets having their normal atypically-small detection radius (Which is actually larger than what everyone else is reduced to in these missions), making it actually feasible to sneak about if you're careful without having to rely specifically on Reapers. These missions also have an 'alertness' mechanic; hitting the maximum alert level of 10 causes infinite waves of reinforcements to start spawning. Each time one of your soldiers is spotted or an enemy is killed, the alert level goes up by 1, and if you fail the hacking roll or pick up the soldier you're rescuing these both shove the alert level straight to 10. Basically, if at all possible try to sneak your way to the prisoner, and then arrange to have everybody sitting at maximum action points when it's time to grab the prisoner and run. Preferably also bring a Specialist to hack the door, though once you have Reaper Infiltration purchased a Reaper is an okay alternative if eg your Specialists happen to all be Tired or wounded. (Or you can just blast a hole in the cell walls; explosions don't inherently raise the Alert Level)
If you have Lost and Abandoned turned on, it's guaranteed you'll get a version of this pretty much immediately after the Lost and Abandoned mission, specifically to retrieve/recruit Mox. If you don't have Lost and Abandoned turned on, a given run may never see this; it'll only generate if soldiers are Captured, which is mostly pretty easy to avoid; don't let Chosen Capture soldiers, and don't send soldiers on Covert Ops with a Capture Risk unless you negate it. I think soldiers who end up MIA will also automatically be Captured and so potentially you can rescue them, but it hasn't cropped up organically in my runs and it would be a pain to manually test so don't quote me on that.
In practice even if Personnel Extraction generates it's depressingly likely to not be worth it. The most likely period for Captures to occur is in the mid-early game; in the very early game, Chosen won't go for Captures at all, and in the late game you probably have a strong enough squad that good play will very consistently prevent them from getting a chance at Captures, and indeed only rarely give them a chance to act more than once, if at all.
A soldier captured from the mid-early game, if they aren't specifically a Resistance soldier, probably isn't important; they won't be very high level, you won't have had the opportunity to discover they have a combination of bonus skills you love, and if they have a Bond it's probably just a level 1 Bond to some other unimportant soldier. By the time the game gets around to offering you Personnel Extraction, it may well be the case that you're running around with Majors and Colonels, only occasionally dipping as low as Sergeant, and the unfortunate soldier is a Lieutenant not worth the bother.
Being Captured by Covert Op doesn't do a lot to help make Personnel Extraction relevant. Normally you can just send Squaddies off to risk going missing, and usually should; only the Chosen hunting chains can lead to you risking a higher-level soldier being Captured by a Covert Op, realistically speaking, and in most runs it simply won't happen unless you're careless. Sure, you could rescue a Squaddie, but callous as it is to say from an in-universe standpoint, the mechanics strongly discourage bothering; just hire a Rookie and have the GTS train them. It's not like 25 Supplies is a burdensome cost past the early game.
That said, DLC is an important factor here, including your settings. If you have the Tactical Legacy Pack and have unlocked the TLP weapons, odds are actually pretty decent that a soldier captured by the Chosen was carrying an irreplaceable weapon that's moderately valuable. If you have Alien Hunters and either didn't turn on Integrated DLC or heavily prioritized getting the Proving Ground up and building the Alien Hunters gear, it's even more likely that a one-of-a-kind piece of gear was stolen, and the value is more clearly important than with TLP gear, which can be replicated or even outclassed depending on your Weapon Attachment situation. The only caveat to this is that the Bolt Caster's value drops off so tremendously as you advance that if the Captured soldier was only carrying it... well, yes, it's a one-of-a-kind weapon, but it's not worth the bother of retrieving. The Alien Hunters armors are also relevant here; without Integrated DLC, you'll be forced to kill the Viper King fairly early in a run, possibly before your primary Chosen is ready to attempt Captures, thus ensuring the Serpentsuit can potentially be stolen. Even with Integrated DLC, it's still plausible to end up with someone Captured while wearing the Serpentsuit or R.A.G.E. Suit, both of which are valuable enough to be worth retrieving.
Shen's Last Gift doesn't really factor into this, as SPARKs cannot be Captured (Except maybe by being MIA? I doubt it, but if MIA does lead to a Capture, it's at least theoretically possible...) and it doesn't unlock any gear for standard soldiers.
Point being, Personnel Extraction is slightly more likely to be relevant if you have DLC than if not, more so if that DLC is Alien Hunters than if it's Tactical Legacy Pack.
This is actually a good example of a broader trend, that War of the Chosen's design really makes a lot more sense in the scenario of unique, useful gear being generated semi-regularly, but the game doesn't do that by default. If there was more in the way of stuff like a Unique Blacksite Trophy Weapon, a Captured soldier would be a lot more likely to have something valuable and irreplaceable taken with them, and a bunch of other War of the Chosen design elements, like Ambush Risks forcing you to tie up gear on soldiers temporarily, would also benefit. I find it understandable War of the Chosen didn't end up hitting on this idea -it was insanely ambitious as was- but it does have me wonder if XCOM 3 will take a similar design, and if so whether they'll think to include such unique gear. Preferably randomized, for run variety.
Sabotage
Removes two blocks of Avatar Project progress.
Takes 168-240 hours (7-10 days) by default, 288-360 (12-15 days) on Legend.
This will first remove blocks of progress not tied to particular facilities, and then if none remain it will start removing from random Avatar Project facilities. Amusingly, it can actually remove all the blocks a given facility has, leaving the facility intact.
Though I've occasionally had it removes blocks from a Facility even though the main bar had blocks still. It's very rare and I'm not entirely sure what causes it, but it's a possibility to keep in mind.
This tends to be a fairly dangerous Covert Op, frequently having either or both of Capture and Ambush chances in addition to the usual Injured Risk, but it's completely worth it. Knocking off two blocks of Avatar Project progress is basically buying you something close to a month of time before you need to hit an Avatar Project Facility or a plot mission to avoid a game over. That can be the difference between going in with a squad made of Tired soldiers and low-level soldiers, all of whom would be equipped with better armor or weaponry if only you'd been able to wait a week for research to complete/the Supply Drop to hit/whatever, all of which of course leads to a disaster of a mission, vs getting to wait for your elites to be rested and uninjured, your latest technology to come online, maybe even to have dealt with one of the Chosen who would otherwise have jumped you in that particular plot mission.
This is especially important if you have Alien Hunters and run with Integrated DLC turned on, since a mad rush to hit an Avatar Project Facility will likely mean being forced to fight an Alien Ruler before you're really ready to stomp them. Not so bad if your most convenient Facility is guarded by the Viper King, but if you end up forced to pick a fight with the Berserker Queen when you're not even finished transitioning into magnetics, or pick a fight with the Archon King pretty much immediately after he's spawned? That is basically guaranteed to be a disaster that gets people maimed, potentially even killed.
In general, though, basically every run should prioritize this as soon as possible at least once.
On that note, it's worth pointing out that you can't be offered Sabotage until after the Spokesman has revealed the Avatar Project exists. You're not going to do one right away.
To be honest, I feel Sabotage probably should've only knocked off one block per performance. Using a Covert Op to buy time is nice design, but 2 blocks is such a big deal it can easily render the Avatar Project a limpwristed threat. Either that or it should've been limited some other way, such as only being offered once per run per faction. This is a bit too powerful, in any event.
Facility Lead
Provides a lead on an Avatar Project Facility, allowing you to assault it even if you haven't made contact with the region containing it.
Takes 168-240 hours (7-10 days) by default, 288-360 (12-15 days) on Legend.
Note that this is specifically providing the Facility Lead item that you must then burn lab time and Intel on to actually open the ability to attack a Facility. This is a less-than-stellar deal: you should always prefer to perform Sabotage over a Facility Lead unless your goal is specifically to try to attack an Alien Ruler, or I suppose if a Facility happens to have three blocks attached to it Facility Lead might be worth considering. Do keep in mind you don't get to pick which Facility to attack though, so unless there's only one Avatar Project Facility on the map you can't count on getting what you want out of it.
You may still end up with the bad luck to need to urgently lower Avatar Project progress while not having access to Sabotage and find yourself taking Facility Lead because it is available, but this is a circumstance to be avoided. Consider Sabotaging earlier than you expect to need it if Sabotage spawns early on, so you don't have to rely on a later month happening to have Sabotage.
Bizarrely, I'm given to understand this Covert Op is something each Resistance faction will let you perform exactly once in the entire game (That is, if the Templar offer it and you take it, the Reapers and Skirmishers can still offer it but the Templar will never do so again), and also only one of them will offer it in a given month. This is especially bizarre since Sabotage is not held to an equivalent limitation (I've repeatedly had all three factions offer it at once, and absolutely ground the Avatar Project's progress into dust with repeated Sabotages, so I know this is true for a fact), while being vastly more general and effective. If this is true, what the heck Firaxis?
Above and beyond that baffling set of details, this is just a bad Covert Op you should basically only ever turn to out of desperation, by virtue of you having absolutely no other way to avert an Avatar Project-caused game over. Avatar Project Facility Leads don't even sell for much; a meager 20 Supplies if the Black Market is particularly interested in it!
I don't really get why this Covert Op was made so gratuitously bad.
I do like the image, at least, as it's indicating without explicitly saying so that you get a Lead by virtue of an ADVENT soldier tattling. It's one of War of the Chosen's better touches for indicating that ADVENT soldiers aren't universally willingly, knowingly complicit with the regime's awfulness.
Like Sabotage, this can't be offered prior to the first Avatar Project Facility being revealed. Not sure if a Facility being present in general is necessary for it to be on offer, though. Regardless, this is one more reason it's underwhelming; if you could grab it preemptively, you could at least hit the first Facility way faster than you're supposed to be able to, and this would ease the pressure on you fairly dramatically since Avatar Project Facilities speed up the Avatar Project bar so long as they're present. As-is?... Sabotage can be offered sooner, in addition to all the other ways it's better, since the first Avatar Project Facility is built noticeably later than the Avatar Project being revealed!
Counterintelligence
Counters a Chosen's monthly activity.
Takes 168-240 hours (7-10 days) by default, 288-360 (12-15 days) on Legend.
A given faction will only ever provide one Counterintelligence per month, which will always match to whichever Chosen they are the Adversary of. Also note that while you might intuitively expect Counterintelligence to go away once the relevant Chosen completes their monthly activity, this doesn't happen; if you're not sure whether the relevant Chosen has already implemented their action or not, don't be performing Counterintelligence, it may be a waste of time.
Counterintelligence should usually be ignored. It's one of the more dangerous Covert Ops, tending to have all three Risk types at a High rating, it's one of the slower Covert Op types, and most of the time what's being blocked is a Retribution or occasionally Sabotage attempt. Retribution is just plain not worth blocking; slowing Knowledge gain from Chosen activity isn't particularly valuable in and of itself, whereas if you care about the lost Supplies Helping Hand will be faster while generally being about as dangerous and having essentially the same effect. (Reminder: Helping Hand is terrible. It's still better than blocking a Retribution!) Chosen Sabotage is more worth considering blocking if you don't have a Defense Matrix up, as some of its consequences can be pretty nasty, but most of the time its effect will be essentially ignorable, and if you have a Defense Matrix up it will probably fail anyway. Training, meanwhile, can't be blocked.
That leaves Chosen Dark Event and Avenger Assault as seriously worth blocking while being possible to block... and there is absolutely no guarantee you'll be offered Counterintelligence when either one is lined up. Indeed, my experience is that most months I only have one Counterintelligence option at all, though this isn't a hard rule; I have occasionally had all three Resistance factions offering Counterintelligence at once. Anyway, point is it's actually pretty rare for you to be offered the ability to block either of those.
If you do get the option for blocking Chosen Dark Event, that is 100% worth considering, since the only other way to block it is to permanently take out the Chosen beforehand. If the Dark Event is something fairly nasty, and you can block it? Go for it, and indeed prioritize it because otherwise you'll miss your chance. Even if it's not particularly threatening, if you're playing with Grim Horizon on you may wish to block it if possible anyway, just to avoid stacking on yet another permanent Dark Event.
The Avenger Assault is a judgment call issue. If your team is all well-rested and uninjured, your technology is keeping up or even pulling ahead of overall enemy threat level, and you've got a great set of Bonds... it's honestly probably better to let the Avenger Assault through. You'll get a ton of bodies for loot, you'll get experience on 10 soldiers instead of the usual 6, and fighting off the attack will cause all Chosen Knowledge levels to drop by around a full level, reducing Risks on Covert Ops and potentially causing one or two Chosen to be unable to initiate more threatening activities.
On the other hand, if Fatigue and injury crunch is at its peak, your technology is behind the curve, and you desperately need to knock back the Avatar Project clock meaning you can't give your soldiers a rest, and you can block an Avenger Assault with a Covert Op? You probably should, to avoid an outright game over.
Overall, though, the vast majority of the time you should probably ignore Counterintelligence. It's just not a good value for the time and risk.
Naturally, this can't be offered unless there's blockable Chosen activity, meaning it will never be offered by a faction if you're not in contact with their Chosen or if said Chosen is dead. So thankfully it doesn't tend to clog up your Covert Ops list.
Technical Advances
Performs a Breakthrough.
Takes 120 to 168 hours (5-7 days) by default, 192-288 (8-12 days) on Legend.
Technical Advances is, assuming the Breakthrough is any good, basically an automatic thing to take. They tend to be pretty low-risk Cover Ops, and then the payoff is (Usually) a permanent improvement that cannot be taken from you. Generally the first thing I try to do when the month rolls over is look for Technical Advances and then try to clean them out if they're not the dubious cost-savings ones, and then possibly go after Resistance Orders from there.
Technical Advances also always demands a Scientist, eating the second slot you'd usually use a soldier for, and so by default you can't speed it up with a Bond pair. As far as I can tell, having a Scientist out on a Covert Op provides no penalty to your research, and even though the game has the ability to injure your Scientists and Engineers, the Injury chance on Covert Ops will never hit your non-combat personnel. As such, this Scientist requirement is a joke, only having any possibility of mattering if you've already built a Laboratory while having only 1-2 Scientists or maybe if a Chosen Sabotage attempt happened to wound a Scientist under the same conditions but with an extra Scientist. (Because a Scientist on a Covert Op can't man a slot in the Laboratory, and so that will slow your research a little)
By a similar token, there's really no cost to having Scientists negate Risks on a mission, not even from Ambushes as I noted earlier. The only issue I've ever run into is that researches actually have minimum Scientist requirements and a Scientist on a Covert Op is not counted for whether you reach that minimum or not, but it's really rare for this to crop up; you basically have to send your very first Scientist out on a Covert Op simultaneous to something like hitting the Instant threshold for the Sectoid Autopsy. (Which requires 1 Scientist to be allowed to do)
Note that Technical Advances can totally have a third slot for negating a Risk, and so you can still potentially have a Bond pair hurry it up, it's just not guaranteed.
Anyway; this is in fact the preferred way to acquire Breakthroughs, weirdly enough. Notably, while the base timeframe is equal to or greater than lab time for a Breakthrough below Legend, manning the Resistance Ring will drag even a high rolled duration down to below normal Breakthrough time. Meanwhile Covert Operators can potentially shave another day off Technical Advances! That can be a 3-day Breakthrough below Legend, as opposed to the normal 5. Furthermore, Breakthroughs are not sped up by Scientist counts or the presence of a Laboratory, so this relationship never shifts in favor of lab time being spent on Breakthroughs. Meanwhile, research is essential to advanced core technologies and gaining the ability to advance the plot, things Covert Ops can't be spent on; you can't perform a Covert Op to unlock Plasma and Shadow Lances, for example.
There are times it can be worth considering spending lab time on Breakthroughs, but it's not the preferred thing; Covert Op time is the better choice.
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Additionally, there's a Covert Op labeled 'Delay Chosen' in the files that takes from 120-168 hours normally, 192-288 on Legend, which I've never actually seen in-game. My best guess is that it was a Covert Op to knock back a Chosen's Knowledge Level, which got cut because that would rather undercut the pressure they're supposed to put the player under, much like how being able to sabotage the Avatar Project via Covert Ops and a Resistance Order makes it surprisingly easy to stall that clock. The following is its duration in the config files;
Takes 120 to 168 hours by default, 192-288 on Legend.
I dunno, it's possible it exists and I've simply never managed to see it in literally hundreds of hours of play, but I'd be quite surprised if this were so.
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So that's Covert Ops; a major new system with a lot of implications that is, after the Fatigue system, honestly probably the most influential single system added by War of the Chosen.
Up next, we cover those Breakthroughs I was just mentioning.
See you then.