Achaea was founded in 1205 by William of Champlitte, a minor knight who had participated in the crusade. It became a vassal of the Kingdom of Thessalonica, along with the Duchy of Athens, until Thessalonica was captured by the Despot of Epirus in 1224. After this, Achaea became the dominant power in Greece.
Achaea was rather small, consisting of little more than the interior of the Peloponnese (which the crusaders called Morea) and a few ports such as Monemvasia. It was surrounded by Epirus as well as territory held by Venice in the Aegean Sea, but it was fairly wealthy, and helped the Latin Empire against the exiled Byzantine emperors of the Empire of Nicaea.
The capital of the principality was originally at Andravida. In the mid-13th century the court at Andravida was considered to be the best representation of chivalry by western Europeans. Prince William II Villehardouin was a poet and troubador, and his court had its own mint, literary culture, and form of spoken French. The Prinicipality produced the Chronicle of Morea, a valuable history of the Crusader States in Greece. Achaea's laws became the basis for the laws of the other Crusader States, combining aspects of Byzantine and French law, and nobles often used Byzantine titles such as logothetes and protovestarios, although these titles were adapted to fit the conceptions of Western feudalism. The Byzantine pronoia system was also adapted to fit Western feudalism; peasants (paroikoi) technically owned their land, but military duties and taxes that they had not been subject to under the pronoia system were imposed on them by their new French lords. Essentially, the early Principality was a little French colony.
William II moved the capital of Achaea to Mistra, near Sparta, in 1249. In 1255 he began a war against the Venetian territories in the Aegean, and in 1259 he allied with Manuel II, despot of Epirus, against Michael VIII Palaeologus of Nicaea. However, Manuel then deserted to join Michael, and William was taken prisoner. After Michael recaptured Constantinople in 1261, William was released in 1262 in return for Mistra and the rest of Morea, which became a Byzantine despotate.
After William, the Principality passed to Charles I of Sicily. In 1267 Charles was given Achaea by Baldwin II of Constantinople, who hoped Charles could help him restore the Latin Empire. Charles and his descendants did not rule in Achaea personally, but they sent money and soldiers to help the principality defend against the Byzantines. In 1311 the Duchy of Athens was taken over by the Catalan Company, whose actions helped to destablize Achaean territory. Achaea came under the control of Italian nobles, who held on to the increasingly smaller territory for another century before it was conquered by Thomas Palaeology, the Byzantine despot of Morea, in 1432. The Byzantines held it for less than 30 years, until the area was taken by the Ottoman Empire in 1460.
Princes of Achaea