Dont use the same broken strategy over and over, the battles are NOT random. They are based on XP, unit type, and surrounding units alliance.
Created Places Easy Win
First make a place any size and and run mountains all the way across the map accept for one space in the middle in that space put a missile silo. Put a bunch of of your troops in front of it to defend it. The enemy will try to push through but hold them off there cause they can only put so many troops through there at once. (Hint:Watch out for aircraft jeeps and some tanks that can fly or drive over the mountains)