Süleyman Çelebi

But when the Ottoman army was defeated, he fled to European portion of the empire, also called Rumelia (or Rumeli), with his father's vizier Çandarlı Ali Pasha.

Afraid of Mehmet's increasing power, Süleyman crossed the Dardanelles strait to reunite the empire.

But before fighting against Mehmet, he marched to the Aegean Region to intimidate the small Turkmen principalities (beyliks of Aydin and Menteşe) which had been annexed by the brothers' father Beyazid I, but had broken free after the disastrous Battle of Ankara.

Because of this plot, Süleyman now had to fight in two fronts on two sides, one in Europe against Musa and one in Anatolia against Mehmet.

However, the Serbs switched sides and joined Süleyman's forces, and Musa was defeated in the Battle of Kosmidion on 15 June 1410.

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

Map of western Anatolia, the Aegean, and the southern Balkans, with states marked by different colours, and the main cities of the period and rivers
Map of the southern Balkans and western Anatolia in 1410, shortly before Süleyman's defeat. Ottoman and Turkish territories are marked in shades of brown, Byzantine territory in pink, and Venetian and Venetian-influenced areas in green