The Nagasaki company was renamed "Mitsubishi Shipbuilding & Engineering Company, Ltd." in 1917 and again renamed as "Mitsubishi Heavy Industries" in 1934. It became the largest private firm in Japan, active in the manufacture of ships, heavy machinery, airplanes and railway cars. Mitsubishi Heavy Industries merged with the Yokohama Dock Company in 1935. From its inception, the Mitsubishi Nagasaki shipyards were heavily involved in contracts for the Imperial Japanese Navy. The largest battleship "Musashi" was completed at Nagasaki in 1942. The company also housed the Mitsubishi Steel and Arms Works, the Akunoura Engine Works, Mitsubishi Arms Plant, Mitsubishi Electric Shipyards, Mitsubishi Steel and Arms Works, and Mitsubishi-Urakami Ordnance Works, which employed 90% of the city's labor force, and accounted for 90% of the city's industry. These connections made Nagasaki a legitimate target for strategic bombing during World War II by the Allied air forces, which later dropped an atomic bomb on the city on August 9, 1945. This attack, following the atomic bombing of Hiroshima three days earlier, dealt a devastating blow to the Japanese leadership, contributing to the surrender of Japan six days later.