Bayezid I vs Selim 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.

To secure his succession, Selim I ordered the execution of his brothers, Prince Mustafa and Prince Korkut, who were potential rivals for the throne. This act followed the Ottoman practice of fratricide to prevent civil war. It eliminated internal opposition and consolidated Selim's rule.

Selim I led the Ottoman army against the Safavid Empire under Shah Ismail I at Chaldiran in eastern Anatolia. The Ottomans, using superior artillery and gunpowder tactics, decisively defeated the Safavids. This victory secured Ottoman control over eastern Anatolia and prevented Safavid expansion westward.

Selim I led a campaign against the Mamluk Sultanate, defeating them at the Battle of Marj Dabiq and the Battle of Ridaniya. He conquered Cairo and the Hejaz, including the holy cities of Mecca and Medina. This brought the Islamic caliphate under Ottoman control and expanded Ottoman territory into North Africa and Arabia.

After conquering Cairo, Selim I received the keys to the Kaaba and the relics of the Prophet Muhammad from the last Abbasid caliph, Al-Mutawakkil III. Selim I assumed the title of Caliph, claiming spiritual leadership of the Islamic world. This transfer established the Ottoman sultans as caliphs until 1924.