Battle of Leuctra
During the Peloponnesian War, battle engagements became more fluid, light troops became increasingly used, and tactics evolved to meet them. However, in direct confrontations between the two opposing phalanxes, stamina and "pushing ability" were what counted. It was only when the Thebans, under Epaminondas, increased the depth of a part of their formation at the Battle of Leuctra that caused the Spartan phalanx formation to break.