The organization you're looking for is the Indian National Army.

In 1941, Indian nationalist Subhas Chandra Bose had collaborated with Nazi Germany to form the Free India Legion, or Indische Legion. Although the vast majority of Indian POWs refused to join, around 2,000 POWs (out of 15,000 held in German camps) eventually enlisted. Initially part of the Wehrmacht, the Free India Legion eventually became part of the Waffen-SS in 1944 and saw sporadic fighting during the war in Western Europe. The Italians also recruited a similar unit, the Battaglione Azad Hindoustan without Bose's help.

By the middle of the war, Bose already had experience getting Indian POWs to defect and collaborate with the Axis cause.

In 1943, Bose traveled to Japanese-held Sumatra via German and Japanese submarines. He quickly began organizing a second armed force, the Indian National Army (INA), or Azad Hind Fauj with the help of the Japanese.

However, he wasn't the only person who'd tried to create an INA. ex-POW Mohan Singhhad thrown in his lot with the Japanese to form the first Indian National Army. However, Singh had clashed with the Japanese, who he'd felt were exploiting him - in 1942, Singh was imprisoned by the Japanese and his INA dissolved.

Bose revived the INA, recruiting POWs and Indian expats to his new force. About 20,000 POW defectors were joined by another 20,000 volunteers. Some POWs joined to escape Japanese POW camps, some were coerced, and some subscribed to Bose's politics.

The INA went into battle in Burma in 1944, taking part in the U Go Offensive into India. INA officers hoped that they would excite a popular anti-British uprising. They also believed the soldiers of the British-led Indian Army would defect to the INA in large numbers. The opposite happened, the INA were widely-regarded as traitors by the Indian soldiers and captured INA soldiers were often very roughly handled. The U Go Offensive failed with heavy losses and the INA was forced to retreat.

When the Allies went on the offensive in 1945, the INA crumbled and was forced to retreat, having failed to accomplish it's aim. Post-war, the INA were regarded as heroes in India - Singh went to a successful political career (Bose had been died in a plane crash), and the British post-war trials of INA officers came under intense public pressure - several sentences had to be commuted to avoid further public outcry.

If you'd like further reading - Brothers Against the Raj by Leonard Gordon and Peter Fay's The Forgotten Army are both good places to start.

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