The Corinthian War was an ancient Greek military conflict between Sparta and four allied states, Thebes, Athens, Corinth, and Argos, which were initially backed by Persia. The immediate cause of the war was a local conflict in northwest Greece in which both Thebes and Sparta intervened. The deeper cause, however, was hostility towards Sparta provoked by that city's unilateral domination of Greek politics in the nine years after the end of the Peloponnesian War. The war was fought on two fronts, on land near Corinth and Thebes and at sea in the Aegean. On land, the Spartans achieved several early successes in major battles, but were unable to capitalize on their advantage, and the fighting soon became stalemated. At sea, the Spartan fleet was decisively defeated by a Persian fleet early in the war, an event which effectively ended Sparta's attempts to become a naval power. Taking advantage of this fact, Athens launched several naval campaigns in the later years of the war, recapturing a number of islands that had been part of the original Athenian Empire during the 5th century BC. Alarmed by these Athenian successes, the Persians stopped backing the allies and began supporting Sparta. This defection forced the allies to seek peace. The Peace of Antalcidas, commonly known as the King's Peace, was signed in 387 BC, ending the war.