Before the Battle of Ankara, the Byzantine Empire was a mere pawn of outside forces for several decades but after the defeat of the Ottomans by Timur, the Empire – for a short while – became a player in Ottoman domestic politics and intrigue. Sultan Bayezid conquered much territories in Europe and threatened Constantinople from all directions. The Byzantine Emperor
Manuel II Palaiologos supported Süleyman as claimant to the Ottoman throne. They signed the
treaty of Gallipoli with the
Byzantine regent
John VII Palaiologos in 1403, as the emperor Manuel II Palaiologos was traveling in western Europe at the time. By this treaty, Süleyman gave up certain territories along the
Marmara coast, as well as the major city of
Thessaloniki to the Byzantine Empire in return for Byzantine support during the interregnum and declared himself
sultan of the empire in
Edirne, the capital in
Rumeli of the Ottoman Empire. From the evidence presented above, it can be understood that the relationship between the Byzantine Empire and the Ottomans increased dramatically contemporarily. Despite defeating his brother and rival for the Ottoman throne, Musa, at the
Battle of Kosmidion in June 1410, Süleyman's popularity waned. So much so, that when Musa returned to avenge his defeat during the following year, Süleyman's supporters defected to Musa. Süleyman was captured while attempting to escape and was given to Musa's bodyguard, Koyun Musasi, and strangled to death on 17 February 1411. ==The siege==