The Principality of Achaea or of the Morea was one of the three vassal states of the Latin Empire which replaced the Byzantine Empire after the capture of Constantinople during the Fourth Crusade. It became a vassal of the Kingdom of Thessalonica, along with the Duchy of Athens, until Thessalonica was captured by Theodore, the despot of Epirus, in 1224. After this, Achaea became for a while the dominant power in Greece, and in the mid-13th century the court at Andravida was considered to be the best representation of chivalry by western Europeans.
Achaea was founded in 1205 by William of Champlitte and Geoffrey I of Villehardouin, who undertook to conquer the Peloponnese on behalf of Boniface of Montferrat, King of Thessalonica. With a force of no more than 100 knights and 500 foot soldiers, they took Achaea and Elis, and after defeating the local Greeks in the Battle of the Olive Grove of Koundouros, became masters of the Morea. Only the fort of Monemvasia, and the castles of Argos, Nauplia and Corinth under Leo Sgouros held out until his suicide in 1208. By 1212, these too had been conquered, and organized as the lordship of Argos and Nauplia, and only Monemvasia continued to hold out until 1248. William of Champlitte ruled Achaea until he departed for France to assume an inheritance, but died on the way there in 1209. He was succeeded by Geoffrey I of Villehardouin, who ruled until his own death in 1219.
Achaea was rather small, consisting of the Peloponnese peninsula (then known as the Morea), but it was fairly wealthy, exporting wine, raisins, wax, honey, oil and silk. The capital of the principality was originally at Andravida. It was bordered on the north by Epirus and the Duchy of Athens and surrounded by Venetian-held territories in the Aegean Sea, including the forts of Modon and Coron on the Peloponnese.
Geoffrey I divided the territory of his new domain among his followers. The Principality was divided into 12 baronies, each of them consisting of several smaller fiefs, which were both territorial and financial units, each corresponding to an income of 1000 hyperpyra. These were: the barony of Akova (Matagrifon) located in Arcadia with 24 fiefs, of Skorta (in Karytaina) with 22 fiefs, of Nikli and Geraki with 6 fiefs, of Kalavryta with 12 fiefs, of Vostitza with 8 fiefs, of Veligosti, Gritsena, Passava (in Laconia) and Chalandritsa with 4 fiefs, while the barony of Kalamata was retained as a personal fief by the Villehardouins. There were also seven clerical baronies, headed by the bishop of Patras. Extensive estates were also granted to the military orders of the Templars, the Hospitallers and the Teutonic Knights.
The most important secular and ecclesiastical lords participated in the council of the "Grand Court", which was presided over by the Prince. The council had great authority, and its decisions were binding for the Prince. The Principality's higher officials were the chancellor, the Prince's chief minister, the marshal, the constable, the treasurer, the protovestiarius, in charge of the Prince's personal treasury, and the pourveur des chastiaux, who was responsible for the replenishment of the castles.
The Principality also produced a unique set of laws, the "Assizes of Romania", which combined aspects of Byzantine and French law, and became the basis for the laws of the other Crusader States. Several Byzantine titles such as logothetes and protovestarios continued in use, 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.
The Frankish barons were subjected to heavy military obligations. They had to serve four months each year with the Principality's army and further four months of guard duty on various castles. They could not leave the Principality, except with the Prince's permission, and even then had to return within two years and two days or have their property confiscated.
Geoffrey I was succeeded by his son Geoffrey II, who ruled until his death in 1245. By confiscating the ecclesiastical taxes, in the years 1221-1223 he built himself a powerful castle at Chlemoutsi, near modern Kyllini, which he used as his main residence. Because of this, he came into conflict with the Catholic Church, and was briefly excommunicated by the Pope. When John III of Nicaea besieged Constantinople in 1236, Geoffrey II came to the aid of the Latin Empire with 100 knights, 800 archers and 6 vessels.
Under his son and successor, Prince William II Villehardouin, the Principality reached its zenith. William was a poet and troubadour, and his court had its own mint at Glarenza, and a flourishing literary culture, using a distinct form of spoken French. In 1249, William II moved the capital of Achaea to the newly-built fortress of Mistra, near ancient Sparta. In 1255 he became embroiled in the War of the Terciers of Euboea, and in 1259 he allied with Michael II, despot of Epirus, against Michael VIII Palaeologus of Nicaea. However, Michael II then deserted to join the Nicaean side, and William was taken prisoner at the Battle of Pelagonia. After Michael recaptured Constantinople in 1261, William was released in 1262 in return for Mistra and the rest of Laconia, which became a Byzantine despotate, as well as an oath of allegiance to the Emperor.
However, soon after his release, William broke his oath of allegiance, and begun seeking alliances with and help from various Western nations. Informed by the local Byzantine governor of William's actions, Michael VIII sent an army under the command of his half-brother, Constantine, against William, but the expedition was unsuccessful, the Byzantines first being routed at the Battle of Prinitza in 1262 and then, after Constantine's return to Constantinople, suffering a heavy defeat at the Battle of Makry Plagi in 1263.
After William, the Principality passed to Charles of Anjou. In 1267 Charles was given Achaea by the exiled 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.
For this period the principality was under a violent succession dispute, which originated from the dispossessed Latin Emperor Baldwin II's gift of the overlordship of Achaea to Charles I of Sicily in return for support in his attempt to reconquer the throne in Constantinople, an action which ignored the rights of the Villehardouin Princes of Achaea. The Angevin kings of Naples subsequently gave Achaea as their fief to a series of their own relatives and creatures, who fought against Princess Margaret of Villehardouin and her heirs.
Charles II of Naples had at first granted the fiefdom of Morea or Achaea to Princess Isabella of Villehardouin (from the Villehardouin dynasty), but he deposed her in 1307 and granted it to his brother Philip I of Taranto, who in 1313 transferred it to Matilda (or Mafalda, or Maud) of Hainaut, heiress of Isabella of Villehardouin, who was married to Louis of Burgundy, titular King of Thessalonica. But Margaret, younger daughter of William II Villehardouin, claimed her rights from 1307. In 1313 she claimed them again without success and then transferred her rights to her daughter Isabelle of Sabran, wife of Ferdinand of Majorca. The son of Ferdinand and Isabelle, known as James the Unfortunate, was proclaimed prince of the Morea in 1315 under the regency of his father, who conquered the principality between 1315 and 1316 but was defeated and executed by Louis of Burgundy and Matilda in 1316. In 1316 Louis of Burgundy died and King Robert of Naples deposed Matilda and gave the principality to his brother John of Durazzo, to whom Matilda was briefly married under duress before being imprisoned.
From 1331 the feudal lords began to recognize the rights of James, and in 1333 the recognition was total. Then John transferred his rights to his sister-in-law, Catherine of Valois, titular Empress of Constantinople, wife of Philip I of Taranto, whose stepson Robert claimed her rights until 1346 when she died. Then the claim was issued by the son of Philip and Catherine, Philip II of Taranto. In 1349 James was succeeded by his son James IV (II of the Morea). In 1364 Robert of Taranto, stepson of Catherine and eldest surviving son of Philip I of Taranto, died. In 1373 Philip II transferred his rights to his cousin, overlord and former sister-in-law Queen Joan I of Naples, whose third husband James IV of Majorca, when he died in 1375, left her his own claim to the principality, at which point she became more or less uncontested Princess of Achaea. However, when Joan was imprisoned in Naples in 1381, another, much younger, James, James of Baux, grandson of Catherine and nephew of Philip II, who in 1374 had become titular Emperor of Constantinople, used the opportunity and seized Achaea. In 1383, Achaea was annexed by Charles III of Naples, successor and murderer of Queen Joan of Naples, who was the grandson of John of Durazzo, and James of Baux was driven away. In 1383 the Vicary government began, lasting until 1396, under the Durazzo kings of Naples.
In 1404, Ladislaus, King of Naples, installed Centurione II Zaccaria, the lord of Arcadia, as prince. Centurione continued to hold the post until 1430, when invasions by Thomas Palaeologus, Despot of the Morea, forced him to retreat to his ancestral Arcadian castle. He subsequently married off his daughter and heiress, Catherine, to Thomas, and so on his death in 1432, the principality was united with the despotate. In about 1450, his illegitimate son, John Asen, was the focus of rebellions against the despot Constantine Dragases. The Byzantine reconquest proved short-lived, however, as in 1460, the Ottomans conquered the Despotate.
William II, by treaty, ceded Achaea to his overlord, the King of Naples, Charles I, on his death.
Charles II, who had no interest in Greece, appointed the heiress of William II as princess of Achaea, along with her husband as prince, in 1289.
Charles II deprived Isabella of the principality, though she never recognised this, in 1306 and bestowed it on his own son Philip I of Taranto. Philip I of Piedmont gave up his claim in 1307, though both his son James of Piedmont and grandson Amadeus of Piedmont kept the title and the latter was even recognised as prince by the Achaean baronage, though he never succeeded in coming to Greece to take back the fief.
The principality was disputed after the death of Isabella in 1312. In 1313, Philip I of Taranto gave Achaea as a fief to her daughter Matilda of Hainaut. However, Ferdinand of Majorca claimed Achaea in right of Isabella of Sabran, daughter of Margaret of Villehardouin, second daughter of William II.
With the death of Louis, the principality passed by treaty into the hands of his nephew Eudes IV, Duke of Burgundy. In 1320, Eudes sold his rights to Achaea to Louis, Count of Clermont, who sold them in 1321 back to Philip I of Taranto.
In 1318, Matilda was forced to remarry to John of Gravina, younger brother of Philip I of Taranto, who was Philip's vassal.
In 1333, John exchanged Achaea with his nephew Robert of Taranto.
Philip II resigned his rights to sister-in-law, the queen of Naples.
James IV willed his rights to Achaea to Joan I of Naples and thus united the divergent claims.
From 1383 until 1396 there was an interregnum. The principality was sought by five pretenders, of whom none can be considered to have reigned, though the Navarrese Company had great influence and its leader, Peter of Saint Superan, proclaimed himself prince in 1396.
Andreas Palaiologos willed all of his titles to Ferdinand II of Aragon.