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Yazid I was the Umayyad caliph during the Battle of Karbala, a pivotal event in Islamic history. The battle, which took place in 680 CE, saw the forces of Yazid confront those of Husayn ibn Ali, the grandson of the Prophet Muhammad. Husayn's refusal to pledge allegiance to Yazid led to his martyrdom and the subsequent division within the Muslim community between Sunnis and Shias.