Quote Originally Posted by Realturka
Then I found them... on top of a huge cliff...
The game does that sometimes, spawning units in inaccesible places.
Happened to me too, only in my case the situation was the exact opposite : I had the smaller army and half of it was on some high cliff. It was a close fight, using only half my forces while the rest were watching the show from above like the fans at a soccer game.

Quote Originally Posted by Flavius Gonzo
Those battles are tough.[...]
Those battles are impossible to win. I think the OP was talking about those situations when the AI forces can be reached only by fighter planes and ICBMs.