Answer:
(a) Discontent of Indian soldiers: Indian sepoys were paid much less than British soldiers and had little chance of promotion. They were sent overseas against their religious beliefs, and the General Service Enlistment Act (1856) added to their anger. The new Enfield rifle cartridges were believed to be greased with cow and pig fat, which hurt both Hindus and Muslims. Mangal Pandey's revolt at Barrackpore and the rising at Meerut (10 May 1857) began the struggle.
(b) Discontent among rulers of princely states: Lord Dalhousie's Doctrine of Lapse annexed states whose rulers had no natural heir, such as Satara, Jhansi and Nagpur. Awadh was annexed on the charge of misrule. The pension of Nanasaheb Peshwa was stopped and the Mughal emperor was told his successors would lose the title. Rulers like Rani Lakshmibai and Nanasaheb therefore joined the revolt.
(c) Unsympathetic outlook of the British: The British considered Indians inferior and kept them away from high posts. Heavy land revenue ruined peasants and British policies ruined artisans. Interference in social and religious customs and the activities of missionaries made people fear for their religion. All these feelings combined in the freedom struggle of 1857.