According to a chart in the Japanese Maritime Self-Defense Force (JMSDF) Museum in Kure, Hiroshima Prefecture, Japan, the U.S. military placed a total of 10,703 naval mines in Japanese waters during World War Two, of which 4,157 were disposed of during the war and 6,249 have been disposed of since the war ended. As of 17 May 2015, 297 American naval mines from World War Two remain unaccounted for. On that date a mine was discovered and disposed of in the eastern entrance to the busy Shimonoseki Straits between Kyushu and Honshu.
A record of recent mine disposal results lists the following.
- 2008 – 3 mines – off Sanuki City on the Inland Sea; off Kasaoka City on the Inland Sea; and on the Moji side of the Shimonoseki Straits
- 2009 – 2 mines – one on each side of the Shimonoseki Straits
- 2010 – 1 mine – off Uruma City in Okinawa
- 2011 – 3 mines – at Port Island, Kobe; off Kanda Port near Kitakyushu Airport; south of Manjushima, Shimonoseki
- 2012 – 0 mines
- 2013 – 1 mine – Shimonoseki Straits, off Wakamatsu
- 2014 – 1 mine – Shimonoseki Straits, off Shimonoseki
- 2015 – 1 mine – Shimonoseki Straits, eastern entrance
Mine disposal efforts continue to this day.
According to a display map, Japan itself laid 55,347 mines to defend its perimeter: 15,474 along the Tokai and southwestern island chain, 14,927 in the northern Honshu and Shikoku regions, 10,012 along the coast of Kyushu, 7,640 along the south coast of Korea and across the Yellow Sea, and 7,294 around Taiwan. The same map shows that the U.S. laid most of its naval mines in the Inland Sea and along the Japan Sea coast (to destroy economic supply routes).
The museum focused almost entirely on the JMSDF’s minesweeping and submarine capabilities. The Japanese Navy’s significant contribution to minesweeping off Korea during the Korean War was a major factor in its getting back into the good graces of the U.S. military, resulting in the U.S.-Japan Security Treaty signed in 1952 and amended in 1960.