Sepoy mutiny

Due to economic and social in England the Indians were heavily taxed and Lord Dalhousie Governor general of India implemented the policy "Doctrine of Lapse" due to which many kings lost the kingdom. At that time, the soldiers were being given new rifles called 'Royal Enfield'. Soon rumour were spread that grease used in the rifle where made up of pig and cow fats. Because cow and pigs where like gods for the Hindu and Muslims. So the Seopys of British East Indian Company were started revolt against them.

Source : Wikipedia

At the time, one of the British Lieutenant Baugh, was killed by soldier called "Mangal Pandey" in 34th Bengal Native Infantry (BNI). Later he was caught and hanged on April 8, 1857. Meerut was a base of British army there the situation got tensioned and it spread to all place in north India. However in South the Sepoys were loyal. Soon the sepoys were arrested but they were release by the other sepoys in the troop. They rebellion were joined together and captured Delhi and Delhi was in control of sepoys for some time.

However other part of India where in the hands of British and with the force they regained the power in delhi. There was also other reason for the loss of rebellions, they don't have proper leader to guide and also the kings in other part was not supporting the rebels, instead they supported British East Indian Company. However the British government take over the power in India directly and ended 250 years of British East Indian Company power in India. In 1857-58 India is legally considered a colony of British ruled by a viceroy.