When an army is too powerful to fight head on and you have access to Fairies, first save the game and send something to make sure the enemy has no missile attack, no flying creatures, and that the battle has rocks that cannot be walked on. If the conditions are met, buy a full army of Fairy Slingers and send them in. Do not attack immediately. Instead, position the Fairies over the rocks and places Foot Soldiers cannot reach, then attack. If there is a Mage, kill it first. The enemy army will walk toward the Fairies and stand at the edge of the rock while the Fairies attack until the entire army is destroyed. This can be done with any creature that flies and has the opportunity. Dragons can take out a numbers a Archers and then defeat the rest of the army without losing any more hit points.