The siege of UK bases in Basra was conducted and maintained by the Mahdi Army in Basra for most of 2007. Following the reported major failure of the coalition forces, whose purpose was to stabilise Basra and prepare it for the turning over of security to Iraqi government forces, the city was overrun by insurgent forces from three different Iraqi factions including the Mahdi Army, and the British found themselves under major siege in their bases and capable of conducting only limited defence action in armoured convoys.