Common Peace (Κοινὴ Εἰρήνη, Koinē Eirēnē) was the term used in ancient Greece for a peace treaty that simultaneously declared peace between all the combatants in a war. The concept was invented with the Peace of Antalcidas in 387 BC. Prior to that time, peace treaties in Greece were between two combatants or alliances only and had an expiration date after which either side was free to resume hostilities. According to John Fine, before the advent of the concept of Common Peace, "since peace was seemingly considered only a lull in the more normal condition of war, treaties were always bilateral and usually limited to specified periods of time." An example of such a limited peace is the Thirty Years Peace that concluded the so-called First Peloponnesian War.
The first common peace
The Common Peace was a product of a period of Greek history in which increasingly widespread and destructive warfare had led a number of states to think outside of such limited conceptions of peace. From 395 BC to 387 BC, the inconclusive Corinthian War further exhausted a number of states that had already been severely taxed by the Peloponnesian War. In 387, these states agreed to end the war with a new sort of peace.
The Peace of Antalcidas, also known as the King's Peace because of the strong Persian influence it reflected, contained many of the elements that would characterize later common peaces. First among these was the Persian influence on the terms; by the mid-4th century BC, disunity in Greece has allowed Persia to claim a dominant role in Greek politics. A second element that would be passed on to later peaces was an avowal of the principle of autonomy, which stated that all cities should be free and independent. This provision was highly open to interpretation, and another characteristic provision of Common Peaces provided for how it would be interpreted. The Spartans were appointed as guardians (prostatai) of the peace, with the power to interpret and enforce its provisions. This provision amounted to de facto recognition of Sparta's hegemony in Greece, and later treaties would include similar enforcement mechanisms.
Later common peaces
During the course of the 4th century BC, common peaces were signed on numerous occasions, most of which failed quickly. After the first attempted peace in 387 BC, fighting soon resumed and continued until a peace was signed in 375 BC. In 371 BC, another peace conference was held, and a peace was signed by all major parties except Thebes, but conflict between Sparta and Thebes soon resulted in renewed fighting at the Battle of Leuctra. In 365 BC, a peace called the Peace of Thebes was signed, which recognized Thebes instead of Sparta as guardian of the peace. This too quickly failed, but another more lasting peace was signed after the Battle of Mantinea.
Following that peace, the center of conflict in the Greek world began to shift away from struggles between the city-states of the Greek heartland and towards the growing struggle between Athens and Macedon. No common peaces were signed between 362 and 338 BC, when in the wake of Philip of Macedon's victory at Chaeronea, an agreement was signed in which all Greek states joined his League of Corinth in preparation for a pan-Hellenic campaign against Persia.
The notion of a Common Peace was an attempt to resolve the seemingly endless warfare that plagued Greece in the late 5th and early 4th centuries BC. Ultimately, however, it became little more than a tool in warfare and accompanying political maneuvering. Sparta, as appointed guardian of the first peace, used its position to marshall support for its military campaigns. The principal of autonomy, in theory absolute, was in fact applied only as the hegemonic power saw fit; Epaminondas famously pointed out at the peace conference of 371 that Sparta was acting hypocritically by demanding autonomy for the cities of Boeotia while it continued to dominate Laconia. Some later treaties, such as the Peace of Thebes in 365 and the treaty that established the League of Corinth in 338, served as much to certify the rise of a new hegemonic power as they did to declare peace. Common Peaces, therefore, became merely another element of the politicking and warfare that they were meant to end.