The British Indian Army, commonly called the Indian Army during the period of British rule, was the principal military force maintained in British India between 1858 and 1947. Raised from a mixture of pre‑existing presidency forces and new units, the service performed internal security and frontier duties across the subcontinent and provided expeditionary formations to imperial campaigns overseas. Its history is closely tied to the political transfer of power after the Indian Rebellion of 1857 and to the changing military needs of the British Empire.

Organization and composition

The army combined regiments recruited in India with British Army formations stationed on the subcontinent. Units often retained regional, ethnic or caste identities, with well‑known examples including Gurkha, Sikh, Punjabi and various Bengal, Bombay and Madras line units. The officer corps was dominated by British officers for most of the period, though a gradual process of Indianisation increased the number of Indian officers and senior personnel in the early twentieth century. The service included infantry, cavalry (later mechanized and reformed), artillery and a range of support and engineering services, organized into regiments, brigades and divisions for both garrison work and expeditionary operations.

Origins and administrative reforms

The term "Indian Army" was applied at different times to the presidency armies that the East India Company had maintained and, after 1858, to the reorganized forces of the Government of India. The presidency armies of Bengal, Madras and Bombay were a key inheritance of the company era and were progressively integrated into a single administrative framework. Major reforms at the turn of the century, commonly associated with administrative changes under figures such as Lord Kitchener, standardized unit titles, command arrangements and mobilization systems and sought to improve the army's readiness for both frontier policing and expeditionary warfare. For background on the earlier presidency forces see the material on the presidency armies.

Recruitment, identity and the princely states

Recruitment combined volunteers, long‑service soldiers and men recruited under agreements with princely states and local authorities. Regimental esprit de corps and distinct dress, traditions and languages were important elements of identity. Some units were associated with particular provinces or communities while others were formed as composite battalions for service abroad. These links were significant for cohesion but also reflected colonial recruitment policies that emphasised certain martial reputations.

Service in the First World War

Troops from India were deployed widely during the First World War. Indian Army formations and individual units served in Europe, Gallipoli, East Africa and the Middle East. In the Mesopotamian Campaign they fought against forces of the Ottoman Empire and helped secure objectives in what is now Iraq; that campaign forms part of the wider narrative of Indian contributions to the imperial war effort. The global commitments of the army confirmed its role as an expeditionary force for the empire.

Interwar developments and Indianisation

The interwar years saw continued professional development, reductions and reorganizations as the imperial defence posture shifted. Political change in India and growing demands for Indian representation led to reforms in recruitment and promotion. Indianisation of the officer corps proceeded slowly, accompanied by debates over training institutions, commissions and the future role of the army within an evolving constitutional framework.

Second World War and expansion

During the Second World War the Indian Army expanded substantially to meet global commitments. Indian formations fought in North Africa, the Middle East, Italy and extensively in the South‑East Asian theatre, notably in the Burma campaigns against Japanese forces. The large wartime expansion drew on both long‑service soldiers and new recruits, and it transformed the army's scale, experience and operational capabilities.

Army of India and relations with British formations

From the early twentieth century until 1947 the overall military establishment on the subcontinent was sometimes described as the Army of India, encompassing both locally raised Indian Army regiments and British Army units sent from the United Kingdom. This dual structure meant separate legal statuses, recruitment systems and command arrangements, which reflected imperial priorities and the need to keep certain forces under direct Crown control; for discussion see the entry on the British Army in India.

Legacy, partition and successor forces

By the end of British rule the Indian Army had become one of the largest volunteer armies in the world and had left a substantial institutional legacy. With independence and the partition of the subcontinent in 1947, units, records and personnel were divided and allocated to the newly formed armed forces of India and Pakistan. The history of the British Indian Army is studied for what it reveals about colonial military practice, recruitment policies, the impact of global wars on colonial societies and the shaping of modern South Asian militaries.