Mitsubishi Heavy Industries

Mitsubishi Heavy Industries was one of Japan's largest and most important military-industrial corporations during World War II. Its roots lie in the Nagasaki shipyard, leased from the government by Mitsubishi in 1884 and purchased in 1887. The shipbuilding division of Mitsubishi Goshi Kaisha became Mitsubishi Shipbuilding in 1917; in April 1934 it was renamed Mitsubishi Heavy Industries and in June absorbed Mitsubishi Aircraft, becoming an integrated maker of ships, aircraft, engines, rolling stock and machinery. The term "heavy industries" (重工業) is said to have been coined from English by the president, Iwasaki Koyata.

In the years of rearmament the company became a centre of weapons production. Its shipyards in Nagasaki and Kobe built battleships, aircraft carriers, and submarines; Nagasaki completed the Yamato-class battleship Musashi in August 1942, and Kobe specialised in submarines. Its aircraft division at Nagoya produced the A6M Zero fighter (designed by a team under Jiro Horikoshi) and the G4M bomber. Some ten thousand Zeros were built in all, more than half of them under licence by Nakajima. The company operated factories across Japan and was central to Japan's war production. As male workers were conscripted, its plants relied on mobilised students, the Women's Volunteer Corps, conscripted Korean workers and Allied POWs.

The company's plants were prime targets of U.S. strategic bombing. The Nagoya engine and airframe works were damaged by the Tōnankai earthquake of December 7, 1944 and then bombed repeatedly by B-29s from December 13, forcing production to disperse to improvised and underground sites. The atomic bomb dropped on Nagasaki on August 9, 1945 exploded over the Urakami district, wrecking Mitsubishi's ordnance and steel works there and killing many employees and mobilised students, Korean workers among them.

Under the zaibatsu dissolution policy the company was split in 1950 into East Japan, Central Japan and West Japan Heavy Industries; the Mitsubishi name returned in 1952 and the three merged in 1964 to re-form Mitsubishi Heavy Industries. Responsibility for wartime labour mobilisation remains unresolved: in November 2018 South Korea's Supreme Court ordered the company to compensate former conscripted workers and members of the Women's Volunteer Labour Corps, while the Japanese government maintains the issue was settled by the 1965 Claims Agreement. Parts of the Nagasaki shipyard were inscribed on the World Heritage List in 2015 among the Sites of Japan's Meiji Industrial Revolution.