After the fall of Constantinople to Mehmed II, the only free province of the Byzantine Empire was the Despotate of Morea, ruled by two brothers of the dead emperor Constantine XI Palaeologus, Thomas and Demetrius Palaeologus. It was never expected that these two surviving sons of Manuel II Palaeologus would ever rule. Only after the deaths of their older brothers Andronicus, despot of Thessalonica, Theodore, despot of Morea, John VIII Palaeologus, Constantine XI, and two brothers in childhood, were they able to claim the throne.

Twenty years before the fall of Constantinople, Demetrius Palaeologus tried for the first time to take power with military help from Hungary. He escaped to that court demanding protection and military help against brothers who wanted to kill him. After that he made peace with his brothers many times and many times again tried to take power with help from another power: the Turks.

His brother Thomas decided to ally with the west and he married into a low-level Genoese family. During his rule he had good relations with the Pope, Genoa and Venice. Before resigning the title of Despot of Morea to his brother Thomas, Constantine XI with 7000 soldiers conquered all the Latin states in Greece up to the Turkish border. This led to a Turkish invasion of Morea and a return to the status quo in the year 1446. This invasion of Morea and the fall of Constantinople in 1453 was a final moral blow to the two rulers of Morea. For the last 30 years the Byzantine Empire under the command of Constantine XI and Thomas tried to protect Morea by building a wall on the isthmus of Corinth which connected this province with the rest of Greece.

When Mehmed II invaded Morea in 1460, Thomas, who had been fighting with Demetrius for the last seven years, did not have enough soldiers to protect the wall on which so much money and time had been spent in the 15th century. The formal reason for the invasion was to help Demetrius, who had asked for Turkish help to restore him to power. Thomas, after hearing of the invasion, escaped with his family to Italy where he was recognized as Byzantine emperor. Demetrius, however, received news from Mehmed II that he was not to rule the country. The commanders of the garrisons of all the city fortesses in Morea chose to fight or surrender depending on their will. In the last battle of the Roman Empire, 2213 years after the founding of Rome, Graicas Palaeologus, the military commander of the city of Salmenikos defeated Mehmed II, who after a month of siege returned home without conquering that "unimportant city". Next year Graicas received an offer to become general of the republic of Venice and gave up Salmenikos to Mehmed.

After the fall of Morea Thomas lived in Rome, being recongized in all christian Europe as emperor. On Thomas' death that position fell to his son Andreas, born in Mistra after the fall of Constantinople. The Pope gave little financial help to Andreas, and when Andreas died in 1503 no further claim was made to the empire. Long before that year, Andreas had sold his crown right to the king of France.

Demetrius lived in his golden Turkish cage until his death.

Mehmed II conquered the Empire of Trebizond, de facto the last free teritory of the ancient Roman state, in the year 1461.

Bibliography

• Joseph von Hammer "Geschichte des Osmanischen Reiches"
• Edward Gibbon "The History of Decline and Fall of Roman Empire"
• "Byzantium nightfall ( John VIII )" - on balcan language