Crude oil production, an indigenous industry of Yenangyaung, was taken over by the British and put under Burmah Oil monopoly. British Burma began exporting crude oil in 1853. European firms produced 75% of the world's teak. The wealth was however, mainly concentrated in the hands of Europeans. In the 1930s, agricultural production fell dramatically as international rice prices declined and did not recover for several decades. During the Japanese invasion of Burma in World War II, the British followed a scorched earth policy. They destroyed the major government buildings, oil wells and mines for tungsten, tin, lead and silver to keep them from the Japanese. Myanmar was bombed extensively by the Allies.