XCOM is a war of attrition, and what once took mere (in-game) hours or days now takes weeks or months to complete-while enemy attacks are as frequent as ever. The completion time for training your soldiers, researching projects, building facilities and items-pretty much everything across the board-has been ramped up considerably. Long War takes things to another level entirely. XCOM is a difficult game to begin with, punishingly so on everything but the easiest setting. The core idea behind The Long War is to make the XCOM experience-commanding Earth's last line of defense against an alien invasion-more challenging, more rewarding, and as the name suggests, longer. And yes, the mod's been out in beta for more than a year, but a recent major patch added even more content, features, and tweaks.
Yes, there's a version for Enemy Unknown too, but it isn't nearly as good.
XCOM: Long War is a free mod for XCOM: Enemy Within that maintains the core gameplay but overhauls the entire system to add a depth and breadth of soldier customization, strategic options, and much more. And now there's a mod that's so good it makes the expansion pack feel like a tired retread. Its first expansion pack, Enemy Within, added so much amazing content that it made playing the game an entirely new experience. XCOM: Enemy Unknown is a great tactical game from Firaxis games.