In the Second Messenian War, Sparta established itself as a local power in Peloponnesus and the rest of Greece. During the following centuries, Sparta's reputation as a land-fighting force was unequaled.[12] In 480 BC a small force of Spartans, Thespians, and Thebans led by King Leonidas (approximately 300 were full Spartiates, 700 were Thespians, and 400 were Thebans; these numbers do not reflect casualties incurred prior to the final battle), made a legendary last stand at the Battle of Thermopylae against the massive Persian army, inflicting very high casualties on the Persian forces before finally being encircled. The superior weaponry, strategy, and bronze armour of the Greek hoplites and their phalanx again proved their worth one year later when Sparta assembled at full strength and led a Greek alliance against the Persians at the battle of Plataea.
The decisive Greek victory at Plataea put an end to the Greco-Persian War along with Persian ambition of expanding into Europe. Even though this war was won by a pan-Greek army, credit was given to Sparta, who besides being the protagonist at Thermopylae and Plataea, had been the de facto leader of the entire Greek expedition.
In later Classical times, Sparta along with Athens, Thebes, and Persia had been the main powers fighting for supremacy against each other. As a result of thePeloponnesian War, Sparta, a traditionally continental culture, became a naval power. At the peak of its power Sparta subdued many of the key Greek states and even managed to overpower the elite Athenian navy. By the end of the 5th century BC it stood out as a state which had defeated the Athenian Empire and had invaded the Persian provinces in Anatolia, a period which marks the Spartan Hegemony.
During the Corinthian War Sparta faced a coalition of the leading Greek states: Thebes, Athens, Corinth, and Argos. The alliance was initially backed by Persia, whose lands in Anatolia had been invaded by Sparta and which feared further Spartan expansion into Asia. Sparta achieved a series of land victories, but many of her ships were destroyed at the battle of Cnidus by a Greek-Phoenician mercenary fleet that Persia had provided to Athens. The event severely damaged Sparta's naval power but did not end its aspirations of invading further into Persia, until Conon the Athenian ravaged the Spartan coastline and provoked the old Spartan fear of a helot revolt.
After a few more years of fighting in 387 BC, the Peace of Antalcidas was established, according to which all Greek cities of Ionia would return to Persian control, and Persia's Asian border would be free of the Spartan threat. The effects of the war were to reaffirm Persia's ability to interfere successfully in Greek politics and to affirm Sparta's weakened hegemonic position in the Greek political system. Sparta entered its long-term decline after a severe military defeat to Epaminondas of Thebes at the Battle of Leuctra. This was the first time that a Spartan army lost a land battle at full strength.
As Spartan citizenship was inherited by blood, Sparta now increasingly faced a helot population that vastly outnumbered its citizens. The alarming decline of Spartan citizens was commented on by Aristotle.