 Murad's reign was troubled by insurrection early on.The Byzantine Emperor, Manuel II, released the 'pretender' Mustafa Çelebi (known as Düzmece Mustafa) from confinement and acknowledged him as the legitimate heir to the throne of Bayezid I (1389–1402).The Byzantine Emperor had first secured a stipulation that Mustafa should, if successful, repay him for his liberation by giving up a large number of important cities.