The Battle of Karbala began on the night of 27 August 2007 and involved fighting between the Mahdi Army, who provided security for the pilgrims, and police (who were largely members of the Badr Organization) in Karbala, Iraq. Hundreds of thousands of Shia pilgrims gathered in the city for the annual festival of Mid-Sha'ban. Security was high as pilgrims have been killed in previous years by suicide bombers.