In 1913, a 250-ton crane was installed, and the shipbuilding facilities expanded to permit the construction of large warships.

The Imperial Japanese Navy employed some 50,000 people at the Sasebo Naval Arsenal at the peak of World War II, constructing and refitting destroyers, light cruisers, submarines and other various naval vessels.

The 21st Naval Air Arsenal (Dai-Nijuichi Kaigun Kokusho), established jointly at Sasebo and Omura, produced a total of 966 aircraft.

The facilities at Sasebo were used for repairs on the battleships Yamato and Musashi during the Pacific War.

The remaining portion of the shipyards was given into civilian hands with the establishment of Sasebo Heavy Industries in 1946.