Changes

The invasion then sparked what ultimately developed to be the Greco-Persian wars of the 5th century BCE, where Athens played a leading role among the Greek city-states involved. The initial beginning of this war in 492-490 went well for the Persians, as they destroyed the Greek city of Eretria and captured territory in the Cyclades and Thrace. However, at the Battle of Marathon a force of about 10,000 Athenians and Plataeans were able to defeat the Persians, perhaps the first significant victory of the Greeks against the Persians. This created a setback for the Persians as they could not invade Greece for another 10 years. The second invasion of Greece by the Persian army and fleet was much larger, forcing Athens to create alliances, in particular with Sparta. Initially the Persian force was successful at the battle of Thermopylae against the Greek allies, although possibly at great loss. After the battle of Plataea, the Persians were defeated and were forced to retreat once again. From this point Athens and the Greek allies were on the offensive and this begins Athens' leadership in an alliance that eventually formed the Delian league, which continued the wars against the Persians, mostly now in Egypt and Cyprus. The excuse that the threat of Persia gave and Athens' wealth proved to be key in Athens consolidating power within the Delian league. This led to strife within the league, as the Greek cities began to revolt against Athens increased consolidation of power. Under the Athenian Pericles, the Athenians moved the treasury of the league to Athens. The city also continued to consolidate and take monetary resources, increasing its wealth and power. The cities and regions that followed Athens essentially formed an empire under Athens' leadership. By 460 BCE, tensions were high and the Peloponnesian Wars began as rebellions of Greek cities against Athenian hegemony.