While 15th-century Byzantine historian Doukas described Bayezid as of Albanian origin, modern historian Uzunçarşılı wrote that he was born in Amasya as the son of Amasyalı Yahşi Bey, earning him the epithet Amasyalı, meaning "from Amasya," which implied he wasn't a convert.
[2][3][page needed] This means their grandfather was an Albanian convert to Islam and joined the Ottoman conquest, settling in Amasya.
After the disastrous Battle of Ankara in 1402, when Tamerlane defeated the Ottoman Empire and took sultan Bayezid I prisoner, Bayezid Pasha rescued the 15-year-old Mehmed Çelebi from Tamerlane's forces and brought him to his hometown of Amasya.
This move was in order to avoid a civil war in an empire still reeling from that of the Ottoman Interregnum.
Bayezid's forces met with Mustafa in the area of the future village of Sazlıdere in Keşan, Edirne in central Thrace.