Make sure don't retreat because the more you reatreat the more you make your enemy close to your base, even if your lacking of men use skill cards just attack. And the enemies base and the enemies men will be attack at the same time!
I've talked about how to retreat before. Move entire army slightly backward (press "0" to select all your units), and choose a fodder stack (fast produce and expandable units such as goblin, zombie, taurus, etc.) and order them to move forward. This is especially good when your army consists of large number of ranged units.
