The Grand Mosque seizure occurred during November and December 1979 when extremist insurgents calling for the overthrow of the House of Saud took over Al-Masjid al-Haram in Mecca, Saudi Arabia, during the annual Hajj pilgrimage. The insurgents declared that the Mahdi (the "redeemer of Islam") had arrived in the form of one of their leaders – Mohammed Abdullah al-Qahtani – and called on Muslims to obey him.