Answer:
The unsuccessful revolt by Indian soldiers against British colonial rule in 1857-1858 was the Sepoy Rebellion.
Step-by-step explanation:
The Sepoy Rebellion was a bloody and prolonged uprising against the British East India Company which broke out in May 1857 in India. The uprising was concentrated in northern India and continued until June 1858, although minor fighting continued throughout that year. This led to the East India Company being replaced by direct British rule and the formation of British India formally.
The exact causes of the uprising are the subject of debate. It began as a mutiny among Indian soldiers in British service, the sepoys, but can also be considered to have had the character of rebellion against foreign rule. It was mainly caused by wounded religious feelings and the experience of social injustice, so Hindu and Muslim insurgents united against the Westerners, and planned to overthrow the British rule.