This century is essentially studied from the Athenian outlook because Athens has left us more narratives, plays, and other written works than the other ancient Greek states. From the perspective of Athenian culture in Classical Greece, the period generally referred to as the 5th century BC extends slightly into the 4th century BC. In this context, one might consider that the first significant event of this century occurs in 508 BC, with the fall of the last Athenian tyrant and Cleisthenes' reforms. However, a broader view of the whole Greek world might place its beginning at the Ionian Revolt of 500 BC, the event that provoked the Persian invasion of 492 BC. The Persians were defeated in 490 BC. A second Persian attempt, in 481-479 BC, failed as well, despite having overrun much of modern-day Greece (north of the Isthmus of Corinth) at a crucial point during the war following the Battle of Thermopylae and the Battle of Artemisium. The Delian League then formed, under Athenian hegemony and as Athens' instrument. Athens' excesses caused several revolts among the allied cities, all of which were put down by force, but Athenian dynamism finally awoke Sparta and brought about the Peloponnesian War in 431 BC. After both forces were spent, a brief peace came about; then the war resumed to Sparta's advantage. Athens was definitively defeated in 404 BC, and internal Athenian agitations mark the end of the 5th century BC in Greece.
Since its beginning, Sparta had been ruled by a diarchy. This meant that Sparta had two kings ruling concurrently throughout its entire history. The two kingships were both hereditary, vested in the Agiad dynasty and the Eurypontid dynasty. According to legend, the respective hereditary lines of these two dynasties sprang from Eurysthenes and Procles, twin descendants of Hercules. They were said to have conquered Sparta two generations after the Trojan War.
In 510 BC, Spartan troops helped the Athenians overthrow their king, the tyrant Hippias, son of Peisistratos. Cleomenes I, king of Sparta, put in place a pro-Spartan oligarchy headed by Isagoras. But his rival Cleisthenes, with the support of the middle class and aided by democrats, took over. Cleomenes intervened in 508 and 506 BC, but could not stop Cleisthenes, now supported by the Athenians. Through Cleisthenes' reforms, the people endowed their city with isonomic institutions — equal rights for all citizens (though only men were citizens)—and established ostracism.
The isonomic and isegoric (equal freedom of speech) democracy was first organized into about 130 demes, which became the basic civic element. The 10,000 citizens exercised their power as members of the assembly (ἐκκλησία, ekklesia), headed by a council of 500 citizens chosen at random.
The city's administrative geography was reworked, in order to create mixed political groups: not federated by local interests linked to the sea, to the city, or to farming, whose decisions (e.g. a declaration of war) would depend on their geographical position. The territory of the city was also divided into thirty trittyes as follows: