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Sea of Japan


Digital relief map of Sea of Japan

The Sea of Japan lies between Japan and the Asian mainland to the west.  It is an inactive back-arc basin formed behind the Japanese island arc and consists of relatively deep water.  There are only three narrow navigable entrances: Tsushima Strait between Kyushu and Korea, Tsugaru Strait between Honshu and Hokkaido, and La Perouse Strait between Hokkaido and Karafuto.  All three were mined and patrolled by the Japanese throughout the war.

Because the entrances of the Sea of Japan were so well-guarded, the area was a haven for Japanese merchant shipping during most of the war.  The Japanese worked hard but with only modest success at developing commerce routes from Japan to Asia through the Sea of Japan.  This was hindered by the relative lack of good ports on the Sea and by the lack of good rail connections from the Asian coast to the interior.  The Japanese had an ambitious but probably unrealistic goal of developing secure communications by ship and rail through the Sea of Japan, across Manchuria and China, and through Indochina, Thailand, and Malaya to the great base at Singapore and to Burma.  This line of communications would be almost immune to the Allied submarine blockade.

However, American submarines penetrated the Sea of Japan on several occasions.  Because neutral Russian ships regularly passed through La Perouse and Tsugaru on their way to Vladivostok, the American submarines were able to sneak through as well by following the brightly-lit neutral ships. Three small groups of submarines penetrated La Perouse Strait in the summer of 1943, but the loss of Wahoo and its celebrated commander, "Mush" Mortensen, in La Perouse Strait prompted Lockwood to call off any further raids. By June 1945 the development of FM sonar and submarine paravanes allowed submarines to penetrate the minefields around Tsushima, and during Operation BARNEY (9-20 June 1945) nine American submarines rampaged through the Sea of Japan, sinking 57,000 tons of shipping at the cost of submarine Bonefish.  This penetration of "the Emperor's bath tub" caused a sensation in Japan, but came late enough in the war that it actually had little effect on the outcome.

References

Blair (1975)

Cohen (1949)

Morison (1959)

Sasgen (2010)


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