Mine Warfare in WW2 Pacific
Mines are the poor step-son of naval warfare. Although used effectively in the European theater from early in the war, their extensive use was not considered for in the vast Pacific theater. Many US military leaders considered them primarily a defensive measure. Submarines laid offensive mine fields off Indochina and Philippines , but a submarine had to travel thousands of miles and sacrifice torpedo space to carry a few mines. Mine layers were
active in the later Solomons campaign. But it was mine sweeping before every invasion that received the most attention. Once the war moved within aircraft range of the home islands and the force of heavy bombers reached a sufficient number to allow missions for other than for the most strategic targets, mining came up on the agenda.
Early European mining in 1939
- Nov 17. Three German destroyers laid 180 magnetic mines in the Thames Estuary and more were laid by subs on the Humber.
British did not know these were new magnetic mines and were without defensive sweeping capabilities.
- Nov 18. German aircraft laid parachute mines. Merchant ships are striking mines during this period.
- Dec 4 . Battleship HMS Nelson, damaged by mine at Clyde
- Dec 10. Convoys depart weakly escorted and ships strike mines through this period.
Atlantic Coast mining 1942.
Early Pacific War Mining.
- Mine field was placed in French Frigate Shoals after three Japanese flying boats refueled there from a submarine and bombed near Pearl Harbor on March 5, 1942.
- A DD and a troop transport were sunk in our own newly laid minefield off Espiritu Santo, New Hebrides, 4 Aug'42.
- 03Sep'42. Japanese minelayer is damaged by aircraft in Solomons area.
- 25Oct'42. SS Pres. Coolidge (contract liner) sunk by mine arriving Espiritu Santo (Vanuatu) ; troops were rescued, their supplies lost.
Defensive and Offensive Mining. (to discuss)
The large mine laying submarine Argonaut (SM1) was immediately converted to a troop transport submarine. (APS-1) in January 1942.
Late War Mining
12,000 sown in last 4-1/2 months of the war to sink 9.3% of Japanese ship losses in WW2. (2% per month)
Submarines sank 54.7% in the whole war, but most of this were in 1944 after the torpedo
problem was solved and while there was still a Japanese seagoing merchant fleet. (1.3% per month)
Perhaps mining should have begun earlier. Japanese officers agreed that the war would have had to end
one month earlier for each month earlier that intensive mining had begun.
The B-29 program cost more than the Manhattan project. It had been built with the intent of strategic bombing and
The Strategic Bomber Command had to fight for strategic independence fromt theater commanders who wanted B-29s to aid in local priorities. The Navy's request to start strategic mining in January fell into this pattern and the 20th Air Force was equally reluctant to covert their weapon into an auxiliary of the Navy as they had resisted the Army.
Interservice cooperation was of a high order, large numbers of submarines had been assigned as lifeguard stations for B-29s. By that time in the war, there were 1000 B-29s
in the Marshals, each able to carry about the mine load of a submarine. Priorities had to be determined in Washington
Mining was put on the Twentieth Air Force agenda and was put into effect with exhaustion of
the incendiary bombs in the firebombing blitz in early March 1945. Mines were used to close down
the sea routes for reinforcements in support of Okinawa invasion of April 1.
In preparation, the Air Force dropped 1,000 mines in the eastern narrows of Shimonoseki Strait on March 27.
This is the stretch between Honshu and Kyushu and the western doorway between the Inland Sea and the East China Sea and Sea of Japan.
The B-29s came back three days later to close the rest of that Strait. During April, 2,000 more mines were dropped.
Seeing how effective mining was, in May they started laying mine fields off principle port cities, but more successfully, an additional 1,500 mines were laid in the Shimonoseki Straight and off harbors on the west shores of Kyushu and Honshu. An island nation, only 3% of that mountainous land is available for crops and imports are required not only for strategic materials, but for food. Submarines had control of the eastern (Bungo Straight) and northern (Kii Straight) exits from the Inland Sea and convoys through these passages had been under increasingly close monitoring since the beginning of the War. By spring Japan's food supply was reduced to at or below starvation levels. June drops were 3,500 mines in the Inland Sea and the Sea of Japan. By July, Japanese shipping was essentially closed down, while mining strikes were made on the south coast of Korea bordering the shallow Yellow Sea where it had been difficult for submarines to operate.
A mix of mine types were dropped to complicate Japan's frantic attempts to sweep
away the mines and restore imports and inter-island shipping. Acoustic, magnetic, and time delay mines meant that an area might be sweep and still sink ships. Suicide boats were even sent ahead of ships carrying critical supplies.
The result of mining is not just the loss of ships, but lost delivery time as ships remained in port to avoid getting sunk.
Also significant efforts must be expended in mine clearing. This is necessarily a permanent activity and ongoing drain on war fighting, else the first indication that a mine field had been planted is the loss of a ship and then it is not always clear if the explosion was from a mine or a torpedo.
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About this page : Mine Warfare in the Pacific War
Created February 18, 2010
To Do: crate a page to discuss mining them and now : mining of Hai Phong Harbor also ended the Vietman War