A Military Department was created within the Government of the East India Company at Kolkata in the year 1776. Its main function was to sift and record orders relating to the Army that were issued by various Departments of the East India Company for the territories under its control.
With the Charter Act of 1833, the Secretariat of the Government of the East India Company was reorganised into four Departments, including a Military Department. The army in the Presidencies of Bengal, Bombay and Madras functioned as respective Presidency Armies until 1 April 1895 when they were unified into a single Indian Army. For administrative convenience, it was divided into four commands at that point, namely Punjab (including the North West Frontier), Bengal, Madras (including Burma) and Bombay (including Sind, Quetta and Aden).
The British Indian Army was a critical force for the primacy of the British Empire both in India and across the world. Besides maintaining the internal security of the British Raj, the Army fought in many other theatres: the Anglo-Burmese Wars, First and Second Anglo-Sikh Wars, First, Secondand Third Anglo-Afghan Wars, First and Second Opium Wars in China, Abyssinia, and the Boxer Rebellion in China.
In the 20th century, the Indian Army was a crucial adjunct to the British forces in both world wars. 1.3 million Indian soldiers served in World War I (1914–1918) with the Allies, in which 74,187 Indian troops were killed or missing in action. In 1915 there was a mutiny by Indian soldiers in Singapore. The United Kingdom made promises of self-governance to the Indian National Congress in return for its support but reneged on them after the war, following which the Indian Independence movement gained strength.
The "Indianisation" of the British Indian Army began with the formation of the Prince of Wales Royal Indian Military College at Dehradun in March 1912 with the purpose of providing education to the scions of aristocratic and well-to-do Indian families, and to prepare selected Indian boys for admission into the Royal Military College, Sandhurst. Indian officers were given a King's commission after passing out and were posted to one of the eight units selected for Indianisation. Because of the slow pace of Indianisation, with just 69 officers being commissioned between 1918 and 1932, political pressure was applied leading to the formation of the Indian Military Academy in 1932 and greater numbers of officers of Indian origin being commissioned.
In World War II Indian soldiers fought alongside the Allies. In 1939, British officials had no plan for expansion and training of Indian forces, which comprised about 130,000 men (in addition there were 44,000 men in British units in India in 1939). Their mission was internal security and defence against a possible Soviet threat through Afghanistan. As the war progressed, the size and role of the Indian Army expanded dramatically, and troops were sent to battlefronts as soon as possible. The most serious problem was lack of equipment. Indian units served in Burma, where in 1944–45, five Indian divisions were engaged along with one British and three African divisions. Even larger numbers operated in the Middle East. Some 87,000 Indian soldiers died in the war. By the end of the war it had become the largest volunteer army in history, rising to over 2.5 million men in August 1945.
In the African and Middle-Eastern Campaigns, captured Indian troops were given a choice to join the German Army to eventually "liberate" India from Great Britain instead of being sent to POW camps. These men, along with Indian students who were in Germany when the war broke out, made up what was called the Free India Legion. They were originally intended as pathfinders for German forces in Asia, but were soon sent to help guard the Atlantic Wall. Few who were part of the Free India Legion ever saw any combat, and very few were ever stationed outside Europe. At its height the Free India Legion had over 3,000 troops in its ranks.
Indian POWs also joined the Indian National Army which was allied with the Empire of Japan. It was raised by a former colonel of the British Indian Army (Gen) Mohan Singh, but later led by Netaji Subhas Chandra Bose and Rash Bihari Bose. With the fall of Singapore in 1942, about 40,000 Indian soldiers were captured. They were given a choice and over 30,000 joined the Indian National Army. Those who refused became POWs and were mostly shipped to New Guinea. After initial success it was defeated along with the Japanese, but it had a huge impact on the Indian independence movement. Similar organisations were also formed in Germany and Japan.
Upon independence and the subsequent Partition of India in 1947, four of the ten Gurkha regiments were transferred to the British Army. The rest of the British Indian Armywas divided between the newly created nations of India and Pakistan. The Punjab Boundary Force, which had been formed to help police the Punjab during the partition period, was disbanded, and Headquarters Delhi and East Punjab Command was formed to administer the area.
The departure of virtually all senior British officers following independence and their replacement by Indian officers meant many of the latter held acting ranks several ranks above their substantive ones. For instance, S. M. Shrinagesh, the ground forces commander of Indian forces during the first Indo-Pak War of 1947-49 (and the future third COAS) was first an acting major-general and then an acting lieutenant-general during the conflict while holding the substantive rank of major, and only received a substantive promotion to lieutenant-colonel in August 1949. Gopal Gurunath Bewoor, the future ninth COAS, was an acting colonel at his promotion to substantive major from substantive captain in 1949, while future lieutenant-general K. P. Candeth was an acting brigadier (substantive captain) at the same time.
Army Day is celebrated on 15 January every year in India, in recognition of Lieutenant General K. M. Cariappa's taking over as the first commander-in-chief of the Indian Army from General Sir Francis Butcher, the last British commander-in-chief of India, on 15 January 1949. With effect from 26 January 1950, the date India became a republic, all active-duty Indian Army officers formerly holding the King's Commission were recommissioned and confirmed in their substantive ranks.