The labour of millions more Indians contributed to the Allied war effort . Poor working conditions and accidents such as the 1944 Bombay explosion claimed many lives . Strategically , India provided the base for American operations in support of China in the China Burma India Theater . Supplies flowed from India to China overland along the Ledo Road and by air over the Hump . Cities on India 's eastern coast were menaced by Japanese air raids ; Calcutta , for instance , was bombed several times . In 1944 , Japanese forces invaded eastern India in 1944 , suffering devastating losses from disease , malnutrition , and exhaustion
1944 Bombay explosion
1944 Bombay explosion
World War II by country