Kuchum Khan was a prominent leader of the Siberian Tatar people in the 16th century. He ruled over the Kazan Khanate and was known for his resistance against Russian expansion into Siberia. His leadership was marked by efforts to maintain the independence of his people and their cultural identity. Kuchum Khan's reign came to an end when he was defeated by the forces of Yermak Timofeyevich, a Cossack leader, in the late 1580s. This defeat marked a significant turning point in Siberian history, leading to increased Russian control over the region and the eventual incorporation of Siberia into the Russian Empire.