'Interregnum period') was a civil war in the Ottoman Empire between the sons of Sultan Bayezid I following their father's defeat and capture by Timur in the Battle of Ankara on 20 July 1402.

His oldest son, Süleyman, with his capital at Edirne, ruled the recently conquered Bulgaria, all of Thrace, Macedonia and northern Greece.

The second son, İsa Çelebi, established himself as an independent ruler at Bursa[11] and Mehmed formed a kingdom at Amasya.

[15] Meanwhile, the other surviving son of Bayezid, Musa Çelebi, who was captured at the Battle of Ankara, was released by Timur into the custody of Yakub of Germiyan.

During the stalemate in Anatolia, which lasted from 1405–1410, Mehmed sent Musa across the Black Sea to Thrace with a small force to attack Suleyman's territories in south-eastern Europe.

Manuel II Palaiologos, the Byzantine emperor, had been the ally of Suleyman; Mûsa therefore besieged Constantinople.

Mehmed made several unsuccessful sallies against his brother's troops, and was obliged to re-cross the Bosporus to quell a revolt that had broken out in his own territories.