 The early Ottoman Empire had no regulated succession, and according to Turkish tradition, every son could succeed his father.Of Mehmed's brothers, the eldest, Ertuğrul, had died in 1400, while the next in line, Mustafa, was a prisoner of Timur.Leaving aside the underage siblings, this left four princes—Mehmed, Süleyman, İsa, and Musa, to contend over control of the remaining Ottoman territories in the civil war known as the "Ottoman Interregnum".