Prior to the fall of Istanbul to the Ottomans, Byzantium had lost its status as a powerful empire: its land mass holdings had shrunk to the territories of Constantinople, Silivri Castle on the Marmara Shore and several small towns, such as Vize and Misivri. These sites were completely surrounded by Ottomans and the villages just beyond the Constantinople fortresses were left untouched by the Ottomans not because they were strong, but because they were considered insignificant. Constantinople wes the target.

The Byzantine emperors had accepted the sovereignity of the Ottomans and were paying tribute taxes to the Ottomans. In reality,then, the Ottomans were dealing not with Byzantine emperors but with minor Tekfurs (Byzantine princes). In essence, then, the domination of Byzantium was not that of an empire and that Constantinople was more a religious center than the sea of an empire. It was the last and the most powerful stronghold of Christendom in the face of Islam and mounting Muslim military forces. To circumvent its fall, the Pope organised a new Crusade.

However, having been stunned by Ottoman attacks, Byzantium’s most debilitating internal problem was exposed : the rift between Orthodox and Catholic Christians. This division led to insufficient assistance from Europe to defend the crippled empire. In a desperate effort to unify the factions, the Emperor and Patriarch gave in, and in 1439 at the Florance Council, knelt down and offered their allegiance to the Catholic Church, who, with the eminent Ottoman thread, put aside their hundred-year-old conflict and differences. The formal celebration of the agreement was to become the subject of mass protests, however, as the people of Constantinople feared European involvement and sought to defray the resurrection of another Latin era.

After the Florence Council agreement, the powerful Crusade that was formed launched an attack on Rumeli in 1443 and 1444. However, the Ottoman victory at Varna was able to stop the tide of invading Crusaders. Varna was also the battle that determined the fate of Constantinople. Now, the conquest of the city became compelling for the young empire, who perceived Constantinople as an ailing element in the heart of Ottoman land. the decisive link between Rumeli and Anatolia spelt the fall of Constantinople and the rise of Istanbul.