Confidential-Rated Map of Japanese Naval Minefields.
Immediate post-World War II military map of Japan and its vicinity, focusing on American minesweeping activities.
The map key indicates that the mines were Japanese (as many of them certainly were), but it stands to reason that much of the mining around the Home Islands was done by the United States to cut off Japan from the rest of the world (see Operation Starvation).
The key reads:
- Jap Mine Lines Shown Thus:
- U.S. Influence Mine Fields Shown Thus: (As of Aug 1945) [Blue]
- U.S. Minesweeping Completed 20 Nov 1945 Shown Thus: [Purple]
A contemporary user has gone over the map with colored pencil updating many of the minefields with notes indicating they had been cleared.
The map also shows the division of responsibility over the region between elements of the US Navy and the Soviet Union. For instance, Korea is divided along the 38th parallel. Interestingly, the US 5th Fleet is assigned responsibility for the majority of the Sea of Japan, even over coastlines on the Korean peninsula that were under Soviet control.
Clearing naval minefields was a vital preliminary step in the U.S. occupation of Japan, as it allowed for freedom of navigation for various troop and food transports, etc.