The Grand Mosque seizure, also known as the siege of Calamity, was a siege that took place between 20 November and 4 December 1979 at the Grand Mosque of Mecca, the holiest Islamic site in Mecca, Saudi Arabia. The building was besieged by up to 600 militants under the leadership of Juhayman al-Otaybi, a Saudi anti-monarchy Islamist from the Otaibah tribe. They identified themselves as "al-Ikhwan", referring to the religious Arabian militia that had played a significant role in establishing the Saudi state in the early 20th century.