Indian Army during World War II
The Indian Army during World War II, a British force also referred to as the British Indian Army, began the war in 1939, numbering just under 200,000 men. 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.
Source: Wikipedia — Indian Army during World War II (CC BY-SA 4.0)