This thesis is a study of the Bengal Army from c. 1800 to c. 1870. Its central aim is to explain why the majority of the Bengal Army's native troops mutinied in 1857. It begins by comparing the pre-mutiny trends in the Bengal Army to those in its sister armies of Madras and Bombay: in particular the Bengal Army's changing pattern of recruitment, its growing list of professional grievances, the deteriorating relationship between its sepoys and their European officers, its relaxation of discipline and its sepoys' use of caste issues as a smokescreen for other grievances. Then it analyzes the events of 1857: the cartridge question, the conspiracy and the pattern of the mutiny itself. Finally it outlines the deliberations of the post-mutiny Peel Commission and the subsequent army reforms, and puts the Indian Mutiny in the context of the recent historiography of military revolts. Its conclusion is that the essential cause of mutiny in 1857 was not the defence of caste and religion, as is generally supposed, but service issues particular to the Bengal Army.