Military history of India during World War II

The Syria–Lebanon campaign, also known as Operation Exporter, was the invasion of Syria and Lebanon (then controlled by Vichy France, a vassal state of Nazi Germany) in June and July 1941 by British Empire forces, during the Second World War.

The Indian National Army (INA, sometimes Second INA; Azad Hind Fauj lit. 'Free Indian Army') was a Japanese-allied and -supported armed force constituted in Southeast Asia during World War II and led by Indian anti-colonial nationalist Subhas Chandra Bose. It comprised British Indian Army POWs taken by Japan and enlisting civilians in the region. The INA aimed to liberate India from British rule. After winning Japanese assent for its goal, the INA furnished support to the Japanese Army. The Japanese and INA forces invaded India from Rangoon in 1944, and Bose's nominal Provisional Government of Azad Hind declared war on Britain. But losses inflicted by the British in the Battle of Imphal in Manipur caused the invasion to be halted. A long and exhausting withdrawal, accompanied by a lack of supplies, malnutrition, and death, ensued, some victorious soldiers in the Indian Army not taking INA battlefield surrender kindly. The remaining INA was driven down the Malay Peninsula and surrendered to Allied forces in August 1945.

The fall of Singapore, also known as the Battle of Singapore, took place in the South–East Asian theatre of the Pacific War. The Japanese Empire captured the British stronghold of Singapore, with fighting lasting from 8 to 15 February 1942. Singapore was the foremost British military base and economic port in South–East Asia and had been of great importance to British interwar defence strategy. The capture of Singapore resulted in the largest British surrender in history.

The Battle of Imphal (Meitei: Japan Laan, 'Japanese invasion') took place in the region around the city of Imphal, the capital of the state of Manipur in Northeast India from March until July 1944. Japanese armies attempted to destroy the Allied forces at Imphal and invade India, but were driven back into Burma with heavy losses. Together with the simultaneous Battle of Kohima on the road by which the encircled Allied forces at Imphal were relieved, the battle was the turning point of the Burma campaign, part of the South-East Asian theatre of World War II. The Japanese defeat at Kohima and Imphal was the largest up until that time, with many of the Japanese deaths resulting from starvation, disease and exhaustion suffered during their retreat. According to voting in a contest run by the British National Army Museum, the Battle of Imphal was bestowed as Britain's Greatest Battle in 2013.

The Royal Indian Navy (RIN) was the naval force of British India and the Dominion of India. Along with the Presidency armies, later the Indian Army, and from 1932 the Royal Indian Air Force, it was one of the Armed Forces of British India.

The Indian Air Force (IAF) is the air arm of the Indian Armed Forces. Its primary mission is to secure Indian airspace and to conduct aerial warfare during armed conflicts. It was officially established on 8 October 1932 as an auxiliary air force of the British Empire which honoured India's aviation service during World War II with the prefix Royal. After India gained independence from United Kingdom in 1947, the name Royal Indian Air Force was kept and served in the name of the Dominion of India. With the transition to a republic in 1950, the prefix Royal was removed.

The Indian Army during British rule, also referred to as the British Indian Army, was the main military force of India until national independence in 1947. Formed in 1895 by uniting the three Presidency Armies, it was responsible for the defence of both British India and the princely states, which could also have their own armies. As stated in the Imperial Gazetteer of India, the "British Government has undertaken to protect the dominions of the Native princes from invasion and even from rebellion within: its army is organized for the defence not merely of British India, but of all possessions under the suzerainty of the King-Emperor." The Indian Army was an important part of the forces of the British Empire, in India and abroad, particularly during the First World War and the Second World War.

The Provisional Government of Free India or, more simply, Azad Hind, was a short-lived Japanese-controlled provisional government in India. It was established in Japanese occupied Singapore during World War II in October 1943 and has been considered a puppet state of the Empire of Japan.

General Headquarters, India was the headquarters of the Commander-in-Chief, India, who commanded the British military forces in India, including the British Indian Army, after the Kitchener Reforms of 1903. It succeeded Headquarters, India which was the term in use initially after the three Presidency armies had been amalgamated into one force. The Commander-in-Chief answered to the civilian Viceroy of India.

The fighting in the Burma campaign in 1944 was among the most severe in the South-East Asian Theatre of World War II. It took place along the borders between Burma and India, and Burma and China, and involved the British Commonwealth, Chinese and United States forces, against the forces of Imperial Japan and the Indian National Army. British Commonwealth land forces were drawn primarily from the United Kingdom, British India and Africa.