Battle of Ankara
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. After the subsequent Ottoman Interregnum in 1413, when Mehmed Çelebi finally defeated his brothers' claims to the throne, Bayezid Pasha became the official grand vizier under the now-sultan Mehmed I.