Demetrios Palaiologos or Demetrius Palaeologus (; 1407–1470) was Despot of the Morea together with his brother Thomas from 1449 until the fall of the despotate in 1460. Demetrios and Thomas were sons of Byzantine Emperor Manuel II Palaiologos, and brothers of the final two emperors John VIII and Constantine XI. Demetrios had a complicated relationship with his brothers, whom he frequently quarrelled with, usually over the matter of Demetrios's wish to establish himself as the most senior of them and claim the imperial throne for himself.
In 1437, Demetrios accompanied his elder brother John VIII to the Council of Florence, the main objective of which was to unify the Roman Catholic and Eastern Orthodox churches so that Western Europe might be more inclined to lend military aid to the desperate Byzantine Empire. Even though Demetrios was staunchly against a union of the churches, he was brought along as John did not dare to leave him in the east without he himself being present. Demetrios attempted to claim the throne twice, first attempting to take it with Ottoman support in 1442 and then by hoping to be proclaimed emperor after John VIII's death in 1448. Both attempts failed and in 1449, Demetrios was proclaimed as Despot of the Morea by the new emperor, his brother Constantine XI.
John VIII had already made Thomas, Demetrios's younger brother, Despot of the Morea, and Constantine now desired for them to rule jointly. The two despots found it difficult to cooperate and often quarrelled with each other. In the aftermath of the Fall of Constantinople, the death of Constantine XI and end of the Byzantine Empire on 29 May 1453, Ottoman Sultan Mehmed II allowed Thomas and Demetrios to continue to rule as Ottoman vassals in the Morea. Though he never proclaimed himself emperor, some of the Moreots wished to proclaim Demetrios, the oldest living brother of Constantine XI, as Constantine's successor. Thomas hoped to turn the small despotate into a rallying point of a campaign to restore the empire, hoping to gain support from the Papacy and Western Europe. The constant disagreements between Thomas and Demetrios, who supported the Ottomans instead, eventually led Mehmed to invade and conquer the Morea in 1460.
Though Thomas escaped into exile, Demetrios was captured at the despotate's capital, Mystras, and surrendered to the Ottomans on 29 May 1460, exactly seven years after Constantinople's fall. As compensation for the loss of the Morea, Mehmed granted Demetrios lands in Thrace and some islands, which allowed Demetrios to live in relative comfort until he was stripped of his lands and income in 1467 following accusations against his brother-in-law. Shortly after, the sultan granted him an estate in Adrianople, where he lived with his wife, Theodora Asanina. After the death of his daughter and only child, Helena, in 1469 at Edirne, Demetrios retired and became a monk, dying a year later in 1470.
Biography
Early life
As the Byzantine Empire fell apart and fragmented over the course of the 14th century, the emperors of the Palaiologan dynasty came to feel that the only sure way to keep their remaining holdings intact was to grant them to their sons, receiving the title of despot, as appanages to defend and govern. Emperor Manuel II Palaiologos (1391–1425) had a total of six sons who survived infancy. Manuel's eldest surviving son, John, was raised to co-emperor and designated to succeed Manuel as sole emperor upon his death. The second son, Theodore was designated as Despot of the Morea and the third, Andronikos, was made Despot of Thessaloniki in 1408 at just eight years old. Manuel's younger sons, Constantine, Demetrios (born in 1407), and Thomas, were kept in Constantinople as there was insufficient land left to grant them. The younger children; Theodore, Andronikos, Constantine, Demetrios and Thomas were frequently described as having the distinction of Porphyrogennetos ("born in the purple"; born in the imperial palace during the reign of their father), a distinction that does not appear to have been shared by the emperor-to-be John.
Relations between the Palaiologos brothers were not always good. Though the young John and Constantine appear to have got on well with each other, relations between Constantine and the younger Demetrios and Thomas were not as friendly. Demetrios was made the despot of the island of Lemnos in 1422 by Manuel; however, he was not satisfied and refused to live on the island. In 1423, Demetrios fled to the court of King Sigismund of Hungary in 1423 under the pretext of needing protection against his brothers. He was accompanied by two of his supporters, Hilario Doria and George Izaoul, and did not return to Constantinople until 1427.
In 1437, John, now Emperor John VIII, left Constantinople to attend the Council of Florence in an effort to unite the Orthodox and Catholic churches and thus inspire Western Europe to act in the defense of his collapsing empire, threatened by the rapidly expanding Ottoman Empire. John left Constantine, his most trusted brother, and favored heir, as regent in Constantinople. Demetrios, alongside many distinguished Byzantine nobles and church officials (including the Patriarch of Constantinople, Joseph II) accompanied John on his journey to Italy. Although Demetrios was known to be firmly against any plans of reuniting the Orthodox and Catholic churches, he had already shown rebellious tendencies, hoping to become emperor himself with Ottoman support, and could not be trusted to remain in Constantinople or Lemnos when the emperor was away.
While the Council of Florence did achieve a union of the churches, it lasted for several years, concluding in June 1439. John did not return to Constantinople until 1 February 1440 and though he was received with a grand and ceremony, organized by Constantine and Demetrios (who had returned sometime earlier), the news that the churches had been unified stirred a wave of resentment and bitterness among the general populace, who felt that John had betrayed their faith.
Attempts to become emperor
With his tenure as regent finished, Constantine had observed that the other Despots of the Morea (Constantine's former appanage), his brothers Theodore and Thomas, had ruled well without him and he considered that he could serve the empire's interest better if he were closer to the capital. Demetrios now governed a stretch of land around the city of Mesembria in Thrace and Constantine considered the idea that he and Demetrios could switch places, Constantine becoming the new governor in Mesembria and Demetrios being granted the Morea. Constantine thus sent his close adviser George Sphrantzes to propose the idea to both Demetrios and Ottoman Sultan Murad II, who by this point had to be consulted about any appointments.
By 1442, Demetrios had no desire for new appointments, instead eyeing the imperial throne. He had just made a deal with Murad himself and had raised an army, portraying himself as the champion of the anti-unionist cause, which opposed the union of the Catholic and Eastern Orthodox Churches, a cause supported by the Turks, declaring war on his brother John VIII. When Sphrantzes reached Demetrios to deliver Constantine's offer, Demetrios was already preparing to march on Constantinople. The danger he posed to the city was so great that Constantine was summoned from the Morea by John VIII to oversee the city's defenses. In April 1442, Demetrios and the Ottomans began their attack, but they were repulsed and Demetrios was briefly imprisoned. In March 1443, Sphrantzes was made governor of Selymbria in Constantine's name. From Selymbria, Sphrantzes and Constantine would be able to keep a watchful eye on the activities of Demetrios. In November, Constantine gave over control of Selymbria to Theodore, who in turn abandoned his position as Despot of the Morea, making Constantine and Thomas the sole Despots of the Morea.
Theodore died in June 1448 and on 31 October of the same year, Emperor John VIII also passed away. The potential successors to the throne were Constantine, Demetrios and Thomas. John had not formally designated an heir, though everyone knew he favored Constantine and ultimately, the will of their mother, Helena Dragaš (who also preferred Constantine), prevailed. Both Thomas, who had no intention of claiming the throne, and Demetrios, who most certainly did, hurried to Constantinople and reached the capital before Constantine. Though Demetrios was favored by many due to his anti-unionist sentiment, Helena reserved her right to act as regent until her eldest son, Constantine arrived, stalling Demetrios's attempt at seizing the throne. Thomas accepted Constantine's appointment and Demetrios, who soon thereafter joined in proclaiming Constantine as his new emperor, was overruled. Soon thereafter, Sphrantzes informed Sultan Murad II, who also accepted the appointment.
Despot of the Morea
The Fall of Constantinople and early rule In order to remove Demetrios from the capital and its vicinity, Constantine made Demetrios Despot of the Morea, to rule the despotate together with Thomas. Demetrios was granted the despotate's nominal capital, Mystras, and primarily ruled the southern and eastern parts of the despotate, with Thomas ruling Corinthia and the north-west, variously using Patras or Leontari as his capital. During his tenure as despot, Demetrios made some efforts to expand the despotate, seizing the Venetian-held castle of Kastri. With him to the Morea, Demetrios brought a part of the ancient Asen family, which had once ruled the Second Bulgarian Empire. Demetrios married Theodora Asanina, daughter of Paul Asan. Theodora's brother Matthew Palaiologos Asen was appointed as governor of Corinth by Demetrios.
Before his marriage to Theodora, Demetrios had been married either once or twice. His previous marriage(s) had not produced any children. His "first" wife was the daughter of Kantakouzenos Strabomytes, between 1430 and 1435. His "second" wife, possibly the same person as the daughter of Kantakouzenos Strabomytes, was Zoe Paraspondyle and died in March/April 1436.
In 1452, during the preparation stages of the final Ottoman siege of Constantinople, Constantine XI sent an urgent message to the Morea, requesting that one of his brothers bring their forces to help him defend the city. To prevent aid coming from the Morea, Mehmed II sent one of his generals, Turahan Bey (who had raided the Morea twice before) to devastate the peninsula. The Turkish attack was repelled by an army commanded by Matthew Palaiologos Asen, but this victory came too late to offer any aid to Constantinople, which fell on 29 May 1453.