This is not true. The Indian Army was a separate service inside the British Army and its origins are from the Sepoy units that the East India Company recruited. They had a distinguished military history in both World Wars and in all theatres. For example WDF at the start of operation Compass consisted of the 7th Armoured Division and the 4th Indian Division. As a by-product of the mutiny the Divisions were organised into 3 brigades one British and 2 Indian. This is why despite having no British Divisions in Malaya the 90th Argyll and Sutherland Highlanders where the last unit into Singapore. The main recruitment for the Indian army came from the Ghurkas (who live in mountains) and the Muslim and Hindu Military Castes (neither of which live in jungles) as such none of these people had any special ethnic advantages in jungle warfare.