My strategy for all 3 levels was putting 5 trenches on the right side in a curve, with the 2 spear men and 3 unarmed. Then I put the cavalry and the 3 heroes on the left side, but still close to the others. During the battle, I lit the trenches, and kamikazed one of my heroes toward the king. The king was triggered and started to charge, which is when my horse and 2 heroes finished it.