Coal production in selected Asian countries 1900-1945, by country

Throughout the early 20^th century, China, India, and Japan were the three largest coal producers in Asia. Japan had the highest output in all years before the Second World War, and Japan's invasions of China in the 1930s was partly due to its desire to gain access to China's coal resources (there is an observable drop in China's output following the 1937 invasion).
India, on the other hand, was a part of the British Empire during this period, and coal production went largely uninterrupted by the war. Unlike many other European colonies or Indian industries, much of India's coal industry was in the hands of Indian owners, which supplied both international markets and domestic development, and contributed to the growth of the Indian upper classes.