The descendants of the Turkmen notables who had assisted the early Ottoman conquests in Europe support the claims of Mehmed, who rules in Amasya.

With the additional support of the Anatolian Muslim religious orders and artisan guilds…

…Mehmed is able to defeat and strangle his brother Isa Bey of Balikesir in southwestern Anatolia, and seize Bursa.

He now sends another brother, Mûsa Bey, against Süleyman.

The Ottoman Interregnum continues into its second decade, as the sons of the late Sultan Bayezid fight for control of the empire.

Musa has the support of Wallachians and Serbs and Süleyman has the support of Constantinople, but the Serbs change sides and Musa is defeated in the Battle of Kosmidion on June 15, 1410.

Suleyman is a weak prince, however, and to the dismay of his partisans, he begins living in extravagance.

Mûsa leads Turks and Wallachians against his brother Süleyman, having coaxing Süleyman's Serbian and Bulgarian Janissaries over to his side.

Süleyman’s indifference to state affairs has caused him to lose supporters, especially after the death of his able vizier Çandarlı Ali Pasha.

Thus, when Musa marches to Edirne in 1411, Süleyman has almost no one at his side.

He tries to escape to imperial Greek territories, but Musa captures him and orders his strangulation on February 17, 1411.

Musa now declares himself sultan in Edirne and undertakes the reconquest of the Ottoman territories in Rumelia.

Bedreddin, a convert to Sufism (Islamic mysticism) who had in 1383 undertaken the pilgrimage to Mecca, and, upon his return to Cairo, had been appointed tutor to the Mamluk crown prince of Egypt, had then traveled as a Sufi missionary throughout Asia Minor; his communalistic doctrines have made him a popular preacher.

Mûsa now appoints Bedreddin chief military judge.

Mûsa sets his forces to besieging Constantinople, but loses his fleet in the effort.

Still supreme but not officially named sultan, Mûsa musters a large army by falsely charging Greek emperor Manuel II Palaiologos with soliciting Timurid aid.

He uses it to punish the Serbians for their 1406 desertion, then moves against Salonika in 1412.

Following his capture of this city and blinding of its ruler, the son of his murdered brother Süleyman, Mehmed declares himself sultan in both Anatolia and Rumelia, with his capital at Edirne, and sets himself to reuniting and restoring the shattered Ottoman empire.

The Turkish notables, in order to deprive the sultan of the only military force he can use to resist their control, require him to abandon the Kapikulu (Palace Guard), justifying the action on the basis of the Islamic tradition that Muslims cannot be kept in slavery.

Mûsa again besieges Constantinople.

An avenger appears, however, in the person of Mehmed, Bayezid's youngest son.

Backed by powerful non-Ottoman Turkish notables and allied to the Greeks, Mehmed helps to lift Mûsa's siege, wins the Janissaries to his cause, and fights Mustafa twice before …

…defeating him a third time at Camurlu, capturing him, and ordering his strangulation in 1413.