Roman Emperor Frederick III assembled a council of German princes and proposed that 40,000 men be sent to Hungary, where the Ottomans had suffered a crushing defeat at Belgrade in 1456. If the combined forces of Hungary, Aragon, Burgundy and the Holy Roman Empire had been unleashed to exploit the victory at Belgrade, Ottoman control of the Balkans would have been seriously threatened. Despite the Ottomans having secured the position of the two despots in the recent Albanian uprising, the possibility of Western aid to restore Byzantine territory proved too enticing to resist. Thomas sent John Argyropoulos and other envoys to the West in 1456 and even Demetrios, decidedly anti-Latin, softened his attitude towards the West. Demetrios raised the possibility of a marriage alliance with Alfonso of Aragon and Naples, suggesting that his daughter Helena marry Alfonso's grandson. Despite his own views on the Council of Florence, Demetrios even sent his own envoy to Pope Nicholas V's successor, Pope Callixtus III, in 1455; Frankoulios Servopoulos, a known supporter of the Council of Florence. Servopoulos probably arrived in Rome at around the same time as Thomas's envoy, Argyropoulos, and the two envoys travelled through Europe, visiting the same courts, independently of each other. Thomas and Demetrios proved to be incapable of working together even with foreign diplomacy. Moreot civil war and the fall of the Morea In the end, no crusade ever set out to combat the Ottomans. Due to their conviction that help would arrive, and being unable to pay, the two despots had not paid their annual tribute to the Ottomans for three years. With no money coming from the Morea, and the looming threat of Western aid, Mehmed eventually lost his patience with the Palaiologoi. The Ottoman army marched from Adrianople in May 1458 and entered the Morea, where the only real resistance was faced at Corinth, within the domain governed by Demetrios. Leaving his artillery to bombard and besiege that city, Mehmed left with most of his army to devastate and conquer the northern parts of the despotate, under Thomas's jurisdiction. Corinth at last gave up in August, after several cities in the north had already surrendered, and Mehmed imposed a heavy retribution on the Morea. The territory under the two brothers was drastically reduced, Corinth, Patras and much of the north-west of the peninsula were annexed into the Ottoman Empire and provided with Turkish governors, with