According to one version of events while his four brothers were fighting each other during the Ottoman Interregnum, he was held captive in Samarkand (in modern-day Uzbekistan).

Growing overconfident in his abilities, Mustafa decided to cross the Dardanelles and complete his conquest of the Asian side of the empire in Anatolia.

Mustafa gave up his hopes to conquer Anatolia and escaped to Rumeli, with Murad's forces in pursuit.

To cross the strait of the Dardanelles after Mustafa, Murad asked for the help of Genoan vessels, for which he paid an exorbitant price.

[6] Aşıkpaşazade mentions that Mustafa was brought by crawling to the execution place, and that he wanted to say something to Murad, but was hanged without even being given the opportunity.

There were also claims that Mustafa Çelebi managed to escape to Wallachia, then to Cafa, and then returned to Thessaloniki where he participated in the long siege of the city on the side of the Venetian defenders.

[7] Meantime, another Düzme Mustafa was unearthed by Venice, claimed to be the son of Bayezid, and that collaborated with the Venetian navy in the spring of 1425.