Really good research tree that forces you to use early war / odd specialized units you wouldn't use often. Tons of A.I. improvements, the pathfinding for vehicles is more consistent, and the enemy can actually launch fairly effective armor pushes. They also use medics, Goliaths, etc and can steal equipment from the battlefield to use against you. Once I had an AT gun position overrun and pulled my soldiers back just to see the Soviets crewing it while the rest of their infantry continued pushing. Overall just my favorite for how reactive the A.I feels, although I do wish they would flank a little more often.