the Ottoman realm. Therefore, Murad hastily concluded a peace treaty in the Balkans. The Hungarians soon broke the treaty, but at Varna a hastily assembled Ottoman army crushed the Crusaders and left the Balkans at the mercy of Ottoman vengeance. John VIII died in 1448. His reign lasted two decades. His achievement was the continued survival of the Empire. Yet Byzantium was now hanging by a thread. With insufficient military manpower for its own defense, an economy ruined by years of warfare, a depopulated capital, and insufficient territory to provide a basis for recovery, the Empire's position was becoming untenable. John was severely constrained by his circumstances, and proved unable to improve the fortunes of the state. He was succeeded by his brother Constantine XI. The new emperor would be Byzantium's last sovereign ruler. Constantine XI Constantine's reign was short; from 1448 (some sources say 1449) until 1453. Constantine XI, like many of his predecessors who took the Union between Eastern and Western Christendom seriously, lived as a Catholic. Not much is known of his reign, except that he died with his soldiers in the final fight for Constantinople. Defiance, defence and defeat Constantine XI was the Despot of the Morea before his ascension to the throne. From this position, he had continued the aggressive policies of his father and his brothers against the Ottomans and their vassals, the Duchy of Athens, but had been forced to back down by Murad II. In 1451, Mehmed II succeeded his father Murad. Upon his succession to the throne, he received a demand by Constantine XI for subsidies, coupled with a threat to rebel if these were not met. Mehmed II responded with these bold declarations by building a fortress on the European side of the Bosporus in order to better control traffic through the Bosporus. Mehmed II assembled a huge army to assail Constantinople's landward walls — some sources suggest 80,000 soldiers, while others suggest figures as high as 100,000 or even 200,000, including camp followers. A major feature of the Ottoman army was its high-quality artillery. Among others, it featured a number of "super-cannons" built by Orban, a Hungarian engineer who had originally offered his services to Constantine, who rejected them for lack of money. After the rejection of terms of surrender by Constantine, the siege began on April 2, 1453, with Ottoman cannon firing from April 6. The defenders were