The ancient Greeks thought of war as an activity that the gods engaged in. Polemos is an ancient Greek word that means 'war', but it can also mean 'fight', 'battle', or 'quarrel'. In ancient Greek mythology, Polemos was the personified spirit (daemon) and divine embodiment of war and battle. He is very similar to the Olympian war god, Ares.
The enemy is within, so these men play war games and fight amongst themselves. They learn to fight in the gymnasium, and apply what they've learned on the battlefield. Their battles are ritualistic displays of strength, and masculinity. It's all about performance. They are divided into factions: red eagle, white dove, or black raven. The blood is fake.