Taking advantage of a loophole in the London Naval Treaty that placed no restrictions on the number of ships with a displacement of up to 600 tons, Japan started building small ships in the 1930s that were classified as Kaibōkans—originally in Japan, this referred to obsolete ships repurposed for coastal defense needs. The project was developed by Mitsubishi. Kaibōkan No. 40 was built at the Fujinagata shipyard. After the surrender of Japan, the ship was used in the fleets of the Anti-Hitler coalition countries as a minesweeper, and in the August of 1947, she was transferred to the Chinese fleet and renamed Chengan. In 1949, the ship became part of the Republic of China Navy.