
TheKing's Peace (387 BC) was apeace treaty guaranteed by the Persian KingArtaxerxes II that ended theCorinthian War inancient Greece. The treaty is also known as thePeace of Antalcidas, afterAntalcidas, theSpartan diplomat who traveled toSusa to negotiate the terms of the treaty with the king ofAchaemenid Persia. The treaty was more commonly known in antiquity, however, as the King's Peace, a name that reflects the depth of Persian influence in the treaty, as Persian gold had driven the preceding war. The treaty was a form ofCommon Peace, similar to theThirty Years' Peace which ended theFirst Peloponnesian War.
By 387 BC, the central front of the Corinthian War had shifted from the Greek mainland to theAegean, where anAthenian fleet underThrasybulus had successfully placed a number of cities across the Aegean under Athenian control, and was acting in collaboration withEvagoras, the king ofCyprus. Since Evagoras was an enemy of Persia, and many of the Athenian gains threatened Persian interests, these developments promptedArtaxerxes to switch his support from Athens and her allies to Sparta.Antalcidas, the commander of a Spartan fleet, was summoned toSusa, along with thesatrap,Tiribazus. There, the Spartans and Persians worked out the form of an agreement to end the war.

To bring the Athenians to the negotiating table, Antalcidas then moved his fleet of 90 ships to theHellespont, where he could threaten thetrade routes along which the Athenians importedgrain from theBlack Sea region. The Athenians, mindful of their disastrous defeat in 404 BC, when the Spartans had gained control of the Hellespont, agreed to negotiate, andThebes,Corinth, andArgos, unwilling to fight on without Athens, were also forced to negotiate. In a peace conference at Sparta, all the belligerents agreed to the terms laid down by Artaxerxes.

The most notable feature of the King's Peace is the Persian influence it reflects. The Persian decree that established the terms of the peace, as recorded byXenophon, clearly shows this:
King Artaxerxes thinks it just that the cities in Asia should belong to him, as well as Clazomenae and Cyprus among the islands, and that the other Greek cities, both small and great, should be leftautonomous [αὐτονόμους], except Lemnos, Imbros, and Scyros; and these should belong, as of old, to the Athenians. But whichever of the two parties does not accept this peace, upon them I will make war, in company with those who desire this arrangement, both by land and by sea, with ships and with money.[1][2][3]
Ionia and Cyprus were abandoned to the Persians, and the Athenians were compelled to cede their newly-won territories in the Aegean. Equally significantly, the insistence on autonomy put an end to a novel political experiment that had grown out of the war, the union of Argos and Corinth. In what the Greeks calledsympoliteia, the two cities had politically merged, granting all citizens jointcitizenship. They were forced to separate, and the Thebans were required to disband theirBoeotian league. Only Sparta'sPeloponnesian League andhelots were overlooked, as the Spartans, who were responsible for administering the peace, had no wish to see the principle of independence applied there.
The single greatest effect of the Peace was the return of firm Persian control over Ionia and parts of the Aegean. Driven back from the Aegean shores by theDelian League during the 5th century, the Persians had been recovering their position since the later part of thePeloponnesian War of 431 to 404 BC, and were now strong enough to dictate terms to Greece. They would maintain this position of strength until the time ofAlexander the Great (r. 336 – 323 BC). AsMikhail Gasparov states in his bookGreece for Entertainment (Занимательная Греция), "Artaxerxes had succeeded whereXerxes had failed; the Persian King was giving orders in Greece like it was his, and without bringing in a single soldier at that." In short, the treaty placed Greece under Persian suzerainty.[4][5]

A second effect of this "most disgraceful event in Greek history", asWill Durant characterized it,[6] was the establishment of Sparta in a formalized position at the top of a Greek political system enforced by the Great King. Using their mandate to protect and enforce the peace, the Spartans proceeded to launch a number of campaigns againstpoleis that they perceived as political threats. Near at hand, they forced the city ofMantinea in Arcadia, to disband into its constituent villages.[7] The largest intervention was a campaign in 382 BC to break up the federalistChalcidian League in northeastern Greece, as violating the autonomy principle of the Great King's decree. On the way there, in 383 the Spartan commanderPhoebidas, invited by a pro-Spartan faction, seized theTheban Kadmeia (the Theban acropolis) and left aLaconophile oligarchy supported by a Spartangarrison; even the pro-Spartan Xenophon could only attribute the act to madness. The principle of autonomy proved to be a flexible tool in the hand of a hegemonic power.
The King's Peace was not successful in bringing peace to Greece.Pelopidas and companions liberated Thebes in 379 by assassinating the Laconizing tyrants. After the Spartan campaign againstOlynthus in 382-379 BC, general fighting resumed (Boeotian War of 378 to 371 BC) with the revived Athenian naval confederacy and continued, with intermittent attempts to restore the peace, for much of the next two decades. The idea of aCommon Peace proved enduring, however, and numerous attempts would be made to establish one, with little more success than the original. By granting powers to Sparta that were sure to infuriate other states when used, the treaties sowed the seeds of their own demise, and a state of near-constant warfare continued to be the norm in Greece.
[...] the Treaty of Antalcidas in 387-6 B.C. had established a Persian suzerainty over Greece that persisted until the formation of the League of Corinth.