The causes of the Mutiny are complex and are shrouded in legend. The immediate trigger may have been Muslim and Hindu sepoys [native Indians serving in the East India company’s army] objecting to defiling themselves with pig and cow fat respectively when they bit a newly introduced British greased cartridge. But the main cause was the continuing spread of British control over northern India, in particular the annexation of Oudh in 1856. When the initial revolt began at Meerut in May 1857, all those who had grievances against the British joined the rebellious sepoys, and a widespread revolt began. After several massacres of Europeans, particularly at Cawnpore and Delhi, the rebellion was put down without mercy. Delhi was taken by the rebels who proclaimed the decrepit last Mughal Emperor as their nominal leader, and was besieged and successfully stormed by British and loyal Indian troops, whilst at Lucknow a small British garrison and its civilian dependents under Sir Henry Lawrence was besieged by a large rebel force. These ‘original defenders’ were augmented by the First Relief Force under Generals Havelock and Outram which broke through to them, but it was not until 1858 that Lucknow and its surrounding area were finally relieved by forces commanded by Sir Colin Campbell. Many battles, skirmishes and sieges across the northern part of India were carried out in extreme heat, the troops formed into long flying columns which became noted for their rapid marches over long distances. Major operations ended in July 1858 and the Britsh Government assumed direct rule of India from the East India Company.