The Hoplite Reform.
In the Bronze Age, the decisive military fighting was done by "heroes", encountering one another on the battlefield in a manner similar to "showdowns" in lore of the American west. The situation may be reconstructed from the quotation from Homer. As the heroes did the critical fighting, they monopolized political authority as well. As Aristotle notes, however, the more stable and prosperous archaic age encouraged the development of a new and superior military system, the heavily armed and trained band of soldier called hoplites. As hoplites had to provide their own armor and find time to train with the army, they tended to belong to the more well to do in the community. Moreover, as the military power to defend the city depended on the cooperative efforts of the hoplites they were able to gain control of the political system.
Homer: Iliad, 12, 310ff. Two heroes discuss their situation at Troy:
"Glaucos, why are the two of us go greatly honored among the Lycians ([Trojans] with seats of honor, meat, and numerous cups? Why do all men regard us as gods? Why do we hold a vast estate on the banks of the Xantos, suitable both for orchards and for the tilling of wheat-bearing earth? We must therefore stand among the front line of the Lycians [Trojans] and take part in the raging baattle, so that the Lycians [Trojans] who wear strong corselets may say: "Our kings who rule Lycia are glorious men; they eat fat sheep and drink the choicest wine. They also have surely the strength of brave men, since they fight in the front rank of the Lycians.""
Aristotle: Politics IV 1297b 15ff.
Aristotle is
"The first form of constitution which succeeded to monarchy in ancient Greece was one in which the soldiery formed the citizen body. At first it consisted only of cavalry. Military strength and superiority were then the prerogative of that arm; infantry is useless without a system of tactics; and as the experience and the rules required for such a system did not exist in early times, the strength of armies lay in cavalry. When, however, states began to increase in size, and infantry forces acquired a greater degree of strength, more persons were admitted to the enjoyment of political rights. For this reason, the name 'democracy" was given at that time to constitutions which we now call "city-states" (polis).