Sultan Bayezid I, also known as Bayezid the Thunderbolt, was the Ottoman Sultan from 1389 to 1402. He was the son of Sultan Murad I and played a crucial role in expanding the Ottoman Empire. Bayezid is known for his military campaigns, particularly against the Byzantine Empire and the Kingdom of Hungary, which helped solidify Ottoman control in the region. His reign was marked by significant territorial gains, but it ended in turmoil after his defeat by Timur at the Battle of Ankara in 1402. This defeat led to a period of instability known as the Ottoman Interregnum, where his sons fought for control of the empire.