Mining of ore from banded iron formations at Anshan in north China began in 1918. When Japan occupied Northeast China in 1931, these mills were turned into a Japanese-owned monopoly, and the city became a significant strategic industrial hub during the Second World War. Total production of processed iron in Manchuria reached 1,000,000 metric tons in 1931–32. By 1942, Anshan's Shōwa Steel Works total production capacity reached 3,600,000 metric tons per annum, making it one of the major iron and steel centers in the world. Production was severely disrupted during the Soviet occupation of Manchuria in 1945 and the subsequent Chinese Civil War. However, from 1948 to 2001, the steel works produced 290 million tons of steel, 284 million tons of pig iron and 192 million tons of rolled steel. Annual production capacity is 10 million tons of pig iron, 10 million tons of steel and 9.5 million tons of rolled steel. A quarter of China's total iron ore reserves, about 10 billion tons, are located in Anshan.