Planned as a replacement of the older and timeworn Natsushima and Sokuten-classes, the Sokuten-class minelayer (no error, a newer Sokuten replaced an older Sokuten...) was a class of minelayers of the Imperial Japanese Navy (IJN), serving during and after World War II.
The first five vessels were ordered under the Maru 3 Program under the designation H11. They were built and commisisoned between 1937 and 1940. The second production model of the Sokuten-class, numbered H11B, was built between 1939 and 1943 under the Maru 4 Programme. The ships were equipped with a 76mm anti-aircraft gun in place of the twin 40mm machine gun of the earlier 5 ships. The Nuwajima had its ballast tank replaced with a fuel tank for convoy escort operations. These nine vessels were classed in the Sokuten-class in the IJN official documents. A tenth unit was canceled in August 1943.
Sokuten as built:
Hirashima as built:
As stated above, she replaced the twin 40mm machine gun with a 76mm single AA-gun, except for some minor details, she and the other ships built after her looked exactly like the other Sokutens.
Ishizaki as of 1943: