I don’t know whether this has been verified at all, but I get the impression from over two dozen games that the strategic layer is a little on rails. More to the point, I think it’s designed to progress at a measured pace (aside from the story missions that you have control over when you tackle them) with just a touch of randomness (i.e., just when in a month a mission will pop up).
You have abduction missions that pop up in groups of three (or less, if you have only two or fewer countries without satellite coverage) about twice a month so long as you have countries without satellites over them. These missions just affect panic ratings, whether you’ll have the opportunity to receive funding from a nation, and dole out bonus money, engineers, scientists, or soldiers (useful for farming, but more on that later).
In the early months, you’ll just see scout and large scout UFOs. Later on, you’ll see the abduction and supply barge class ships, too. I’ve never seen the large UFOs early, so this seems to be a time-based appearance. (Although, some modders found functional but disabled code that would let you detect and intercept abduction and terror class UFOs as they fly to their missions.)
Battleships also only seem to appear after global satellite coverage is reached, with the mission to scan for satellites and shoot them down.
The game will throw in a Council mission usually at least once a month and a terror mission about every other month.
I’ve stalled at the end of playthroughs (before heading to the Temple Ship) in order to farm abduction missions. If you keep three countries on the same continent without coverage, you can ensure that you won’t lose them to panic increases by keeping the potential for increase all in the same place. The best spot to do this is on the XCOM home base continent since you’ll still receive the continent bonus without needing to have full satellite coverage.
Over many in-game months of farming while stalling to raid the Temple Ship, the above pattern emerges. And once you decide to lock up satellite coverage, you don’t even have to go on missions if you don’t want to. Skipped Council missions don’t affect panic ratings. So long as you shoot down UFOs, you don’t have to raid the crash sites. There’s no consequence for skipping them. The only missions you must do are terror missions because they still affect a country’s panic level.
So from this picture, I don’t get the same sense I did with UFO Defense. I don’t feel like there’s an alien player working toward its own ends by running UFO missions or setting up bases. Instead, I feel like Enemy Unknown is rolling out missions at a specific pace to keep me on track to finish the game.
