Irene of Athens vs Selim I

After the death of Leo IV, Irene became regent for her 10-year-old son Constantine VI. She ruled the Byzantine Empire effectively, reversing iconoclast policies and restoring icon veneration at the Second Council of Nicaea in 787.

Irene convened the Second Council of Nicaea, which condemned iconoclasm and restored the veneration of icons in the Byzantine Church. This council is considered the Seventh Ecumenical Council by the Eastern Orthodox Church.

Irene ordered the blinding of her son Constantine VI, who had attempted to assert his own rule. He was imprisoned and died shortly after. This act allowed Irene to become sole ruler, but it was widely condemned as tyrannical and unnatural.

After blinding her son, Irene ruled as sole empress, the first woman to do so in Byzantine history. She used the title 'basileus' (emperor) rather than 'basilissa' (empress), asserting her authority as a male ruler.

Irene was overthrown by a conspiracy led by Nikephoros, the logothete (finance minister). She was exiled to the island of Lesbos and forced to support herself by spinning wool. She died the following year.

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.