Final answer:
The Sepoy Rebellion was triggered by various factors, including the use of animal fat in rifle cartridges, leading to a significant uprising against British officers by Indian soldiers, which resulted in heavy casualties and led to the British Crown taking direct control of India.
Step-by-step explanation:
Angry sepoys rose up against their British officers in what is known as the Sepoy Rebellion or the Indian Mutiny of 1857. This uprising against British rule was fueled by various grievances, including the use of animal fat in rifle cartridges, which disrespected Hindu and Muslim religious practices. The sepoys marched to Delhi, proclaimed the last Mughal ruler as their leader, and a bloody conflict ensued. The British eventually subdued the revolt, with heavy casualties on both sides, leading to the end of the British East India Company's rule and the establishment of direct British colonial governance over India.