Britain’s exploitation of India up to Partition and ‘independence’ in 1947 went much further than extracting investment and trading revenues and dominating its economy. Just consider the British Indian Army, established under British government control in 1858 after it took over from the East India Company. Manned by colonial Indian subjects, this force was critical for British imperialism’s many battles. In wars large and small, especially those outside Europe, against national liberation movements, uncooperative populations and rival powers, Indian troops greatly boosted the numbers of those who would fight and die for it.
Prior to 1914, British armed forces had largely been used to police the Empire. Since Napoleon early in the 19th century and the Crimean War with Russia in mid-century, there had been little or no direct conflict with other major powers. British policy was to depend upon alliances with others, rather than to maintain a large standing army itself. So it was important to be able to draw upon a force of colonial troops when needed, including for the policing of the British Raj.
Important though they were for British power, Indian troops commonly faced racial discrimination, were looked down upon by white officers and were often used as cannon fodder, while also being given worse grade arms and equipment than regular British troops. Attractive as a cheap military resource for the Brits, these men could nevertheless see enlistment in the army as a reasonable option. There was regular pay and regular food, something not always available in the Indian economy dominated by British Empire interests – as became brutally clear with the Bengal famine in 1943.
At the start of World War One in 1914, British army regular forces numbered less than 250,000, but they had grown to 3.8 million by 1918, including reserves, helped by conscription after volunteers proved insufficient. Over the same period, the British Indian Army grew from around 150,000 to more than one million, of which some 700,000 served overseas, making it a valuable additional force. This latter army fought in Ypres, Loos, Neuve Chapelle and Gallipoli, and in Mesopotamia (roughly corresponding to Iraq today), Palestine, Egypt and East Africa.
Although troop numbers fell back in the 1920s and 1930s, the Second World War and its aftermath saw a further utilisation of Britain’s Indian Army. Battle locations during the war included in North Africa (Tunisia, Libya and Egypt) and Europe (Italy, especially). A good book on this period notes that, in early 1942, “264,000 Indian troops were serving overseas, including 91,000 in Iraq, 20,000 in the Middle East, 56,000 in Malaya and 20,000 in Burma.” By later that year, the Indian army had recruited another 600,000 men, and by the end of 1942 it stood at almost 1.55 million. Another 280,000 were recruited in 1943. By 1945, it had grown to some 2.5 million. This compared to 3.5 million in the British army you will more commonly read about.
Indian troops were, of course, used by the British to push back Japan’s wartime incursions into India itself. But the downside for the Brits in the early 1940s was that many Indian prisoners of war (held by the Axis powers) were ready to switch sides and join versions of the anti-colonial Indian National Army. Japan, in particular, made efforts to attract these forces.
Ahead of India’s independence, the Brits had to be a little cautious, but that did not prevent them from using Indian troops to help put down anti-colonial movements in Malaya, Vietnam and Indonesia. These were efforts by the much-lauded ‘socialist’ Labour Government to restore not just the British, but also the French and the Dutch to their former status. To add to the outrage, Britain also used just-defeated Japanese troops for the same purpose!
Despite demobilisation after 1945, by April 1946, “the Indian army still had two brigades in the Middle East; four divisions in Burma; three divisions in Malaya; four divisions in Indonesia; one division in Borneo and Siam (Thailand); a brigade in Hong Kong; and two brigades in Japan.” A division comprised roughly 10-15,000 men, and a brigade roughly 1,500-3,500 men.
Oh well, that’s enough about soldiers.
 The points below focus on Indian troops, but one should note that the British also used African troops and Chinese labourers in their war efforts. France also made great use of its African colonies. A good book detailing these points for the First World War is David Olusoga’s The World’s War: Forgotten Soldiers of Empire, Head of Zeus, 2014.
 This, the later quotation, and most of the information on Indian troop numbers, are taken from Srinath Raghavan, India’s War: the Making of Modern South Asia, 1939-1945, Penguin, 2017. For the post-1945 period, also see Christopher Bayley and Tim Harper, Forgotten Wars: the End of Britain’s Asian Empire, Allen Lane, 2007. A good online source for the history is here.