Bayezid I

Bayezid I led the Ottoman army to victory at the Battle of Kosovo against a coalition of Serbian and Balkan forces. Both Sultan Murad I and Serbian Prince Lazar were killed, but the battle solidified Ottoman control over the Balkans.

Bayezid I conquered the Bulgarian Empire and much of Serbia, incorporating these territories into the Ottoman realm. These conquests expanded Ottoman control over the Balkans and eliminated major Christian states in the region.

Bayezid I besieged Constantinople, the Byzantine capital, for eight years. The siege was ultimately lifted due to the Mongol invasion of Anatolia, but it severely weakened the Byzantine Empire and demonstrated Ottoman ambition to capture the city.

Bayezid I defeated a large Crusader army from Hungary, France, and other European states at Nicopolis on the Danube. The victory crushed the last major Crusade against the Ottomans and confirmed Ottoman dominance in the Balkans.

Bayezid I was defeated and captured by Timur at the Battle of Ankara. The defeat led to the collapse of Ottoman unity and a period of civil war (the Ottoman Interregnum), ending Bayezid's reign and temporarily halting Ottoman expansion.