The Sepoy Rebellion was a revolt of sepoys (Indian soldiers trained by the British) in 1857 against the British. They had heard rumors that the cartridges for their new Enfield rifles were greased with lard and beef fat. Since the cow is sacred to Hindus, and the pig is abhorrent to Muslims, all the sepoys were outraged, and they mutinied. It was also known as the Sepoy Mutiny or Indian Mutiny and was put down by the British.
The Earth and Its Peoples A Global History, Bulliet et al, 2005.