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, suffering devastating losses from disease, malnutrition, and exhaustion.