The last offensive of the Roman Empire was a campaign led by the Despot of the Morea Constantine XI Palaiologos against the Ottomans in Greece:
Constantinople by the 1440’s was like a city-state within Ottoman territory. But, in the Peloponnese, there was the last province remaining, the Despotate of the Morea – and it was from here that the Despot Constantine would make the last attempt to expand Roman territory by conquest Constantine is well-known for his valiant defense in 1453, but he proved himself an able ruler in the Morea.
One of his first actions was “reconstituting the wall across the Isthmus of Corinth. The Turks had easily breached it in 1423 & demolished it in 1431.” Constantine “with the often reluctant collaboration of the leading men of the district, had it completely restored. It was called the Hexamilion.”
“In the summer of 1444, as soon as work on the Hexamilion wall was finished, he went into action not against the Turks but against his Latin neighbors to the north…He was no doubt encouraged by the news from the western Christian world. The pope’s crusade had set out from Hungary down the Danube towards the Black Sea in 1443. Its progress had alarmed the Sultan Murad, who had other problems to deal with in the east.”
It is likely Constantine knew this was the only chance to expand the Romans would get, they could never face the Ottoman army themselves, but perhaps if they took territory and the crusade was successful, they could retain it. It was a gamble, but the Romans had nothing to really lose. “Constantine invaded Attica. The Duchy of Athens…set up by the Franks after the Fourth Crusade, had seen a variety of foreign rulers. In the early 15th century it was held by the Florentine family of the Acciajuoli, albeit under the suzerainty of the Ottomans.”
Thus, by attacking their vassal, Constantine had declared war on the Turks “The Turks were busy elsewhere. Nerio (ruler of Athens) was unprepared for an invasion. Constantine and his army marched into Attica & forced Nerio to surrender Athens & Thebes and pay to him the tribute which he had been paying the Sultan. The capture of Athens seemed particularly glorious. One of Constantine’s counsellors and flatterers was moved to compare him with Themistocles.” But then the bad news. “The pope’s crusade got no further than Varna on the Black Sea coast. There it was annihilated by the Turks.”
Amazingly, “the news did not deter Constantine. His foray across the isthmus had been remarkably successful.” He received 300 warriors from the Duke of Burgundy, added them to his army, and launched raids into Ottoman Greece. He went into “Thessaly, where the Vlachs and Albanians happily hailed him as their lord.” Another offensive was launched across the Gulf of Corinth by Constantine Cantacuzene – one town of Loidoriki even “changed its name to Cantacuzinopolis.” Constantine Palaiologos even became bold enough to kick a Venetian governor out of Vitrinitza.
However, soon enough the time to face reality had come. “In the winter of 1446 Murad took command of an army said to be have numbered 50-60,000 men…Constantine hurried back to his Despotate. He and his brother Thomas took their stand at the Hexamilion wall which they rebuilt with such optimism. The Turkish army reached the wall on November 27.” Constantine tried to offer peace, but the sultan had no reason to negotiate. Murad had numbers, and lined his army up to attack the entire wall so the defenders would be spread incredibly thin. And, importantly, the sultan had cannons. By “December 10 the Hexamilion was no more than a heap of ruins, its defenders killed or captured.” The only thing that saved the Morea was its many fortified towns & castles which would have taken time to conquer. The Turks took 60,000 prisoners back to Ottoman territory though “The Sultan had only come to chastise the Greeks and to strike terror into them and this he had done with great success.” The last Roman conquest had failed
Source:
The Immortal Emperor by Donald M. Nicol
shadowsofconstantinople.com 