A key military development unique to Greece was the phalanx: a unit of spearmen standing in a dense formation, with each using his shield to protect the man to his left. Each soldier in a phalanx was called a hoplite. Each hoplite had to be a free Greek citizen of his polis and had to be able to pay for his own weapons and armor. He also had to be able to train and drill regularly with his fellow hoplites, since maneuvering in the densely-packed phalanx required a great deal of practice and coordination. The hoplites were significant politically because they were not always aristocrats, despite the fact that they had to be free citizens capable of paying for their own arms. Because they defended the poleis and proved extremely effective on the battlefield, the hoplites would go on to demand better political representation, something that would have a major impact on Greek politics as a whole.
The most noteworthy military innovation represented by the hoplites was that their form of organization provided one solution to the age-old problem of how to pay for highly-trained and motivated soldiers: rather than a state paying for a standing army, the hoplites paid for themselves and were motivated by civic virtue. When rival poleis fought, the phalanxes of each side would square off and stab away at each other until one side broke, threw down their shields, and ran away (by far the deadliest part of the confrontation). The victors would then allow the losers time to gather their dead for a proper burial and peace terms would be negotiated.
By the seventh century BCE, the hoplites in many poleis were clamoring for better political representation, since they were excluded by the traditional aristocrats from meaningful political power. In many cases, the result was the rise of tyrannies: a government led by a man, the tyrant, who had no legal right to power, but had been appointed by the citizens of a polis in order to stave off civil conflict (tyrants were generally aristocrats, but they answered to the needs of the hoplites as well). To the Greeks, the term tyrant did not originally mean an unjust or cruel ruler, since many tyrants succeeded in solving major political crises on behalf of the hoplites while still managing to placate the aristocrats.
The tyrants, lacking official political status, had to play to the interests of the people to stay in power as popular dictators. They sometimes seized lands of aristocrats outright and distributed them to free citizens. Many of them built public works and provided jobs, while others went out of their way to promote trade. The period between 650 – 500 BCE is sometimes called the “Age of Tyrants” in Greek history because many poleis instituted tyrants to stave off civil war between aristocrats and less wealthy citizens during this period. After 500 BCE, a compromise government called oligarchy tended to replace both aristocracies and tyrannies. In an oligarchy, anyone with enough money could hold office, the laws were written down and known to all free citizens, and even poorer citizens could vote (albeit only yes or no) on the laws passed by councils.