The armies of the city-states of Classical Greece consisted of military amateurs. They were called up to war without training or preparation; they formed up and fought as best they could. How could such men be forged into a reliable battle line? Jason Crowley's recent book The Psychology of the Athenian Hoplite presents a persuasive case for the importance of horizontal unit cohesion – the desire of each warrior not to let his buddies down – in the performance of the Athenian hoplite militia. Crowley does not emphasise, however, that this horizontal cohesive force had to make up for an almost complete lack of mechanisms to create vertical unit cohesion. Only the Spartan phalanx had a clear officer hierarchy. No other Greek city-state divided its army's units below the level of the lochos, a formation of several hundred men. My chapter will show that Classical Greek authors from Thucydides to Plato were aware of the need for greater vertical binding of the militia. They urged their fellow citizens to embrace military discipline and to organise both their hoplites and their cavalry into clearly defined units led by an elaborate and respected chain of command. It was very clear from the Spartan example just how beneficial such organisation could be. However, the writings of these authors reveal that even in the final decades of the Classical period militia armies had not adopted the methods they proposed. Extensive drill, and the cohesion that comes with it, became the hallmark of the Macedonian phalanx, which ended the freedom of the Greek city-states with relative ease.