Funmurphys: the Blog

Torpedoes Versus Mines

Strategy page has an interesting article on naval mines.

But I was bugged a bit by these paragraphs:

Naval mines achieved several striking successes during World War II. In the Pacific, naval mines proved more destructive to the Japanese war effort than the atom bombs. During a 10 week period between April and August 1945, 12,000 mines were delivered by American bombers. These destroyed 1,250,000 tons of Japanese shipping (670 ships hit, 431 destroyed). That's 18 mines for each ship hit. The Americans had air superiority, so losses during these 1,500 missions amounted to only 15 planes, most of them to accidents. Had these missions been flown against opposition, losses would have been between 30 and 60 aircraft, plus similar losses to their fighter escorts.

A conventional submarine campaign was also waged against Japanese shipping. Comparisons to the mine campaign are interesting. A hundred submarines were involved in a campaign that ran for 45 months from December, 1941 to August, 1945. Some 4.8 million tons of enemy shipping was sunk. For every US submarine sailor lost using submarine launched torpedoes, 560 tons of enemy ships were sunk. During the mine campaign, 3,500 tons were sunk for each US fatality. On a cost basis, the difference was equally stark. Counting the cost of lost mine laying aircraft (B- 29's at $500,000 each) or torpedo armed submarine ($5 million each), we find that each ton of sunk shipping cost six dollars when using mines and fifty-five dollars when using submarines. These data was classified as secret until the 1970s. It indicates that mines might have been more effective than torpedoes even if the mines were delivered by submarine.

What bugs me is comparing apples and oranges here. The time frames are wildly divergent, and the submarine effort in 1941 & 1942 was nothing like the effort in 1945. There were no 100 submarines, and they were technically far inferior to the later boats, just as the B-29's of 1945 was superior to the B-17s of 1942. For instance, American submarine losses in 1942 were 6 (when submarines were often used to try to stop Japanese fleet movements), while in 1945 they were 7 (when submarines were used almost exclusively for sinking Japanese shipping) - care to guess the difference in Japanese tonnage sunk in those two years? Care to guess how many sub losses in 1942 were from simply running aground? And given the problems with American torpedos up until mid 1943 (they didn't explode) including this time period is especially faulty. Why not compare the results of the two methods over the same time period?

The best point is the one about submarines delivering mines, since submarines could go places earlier in the war that airplanes had no hope of doing - like Japan's inland sea or even coastal areas. Would we have been better off using mines then instead of torpedos? Good question.

Full disclosure - my father served aboard a submarine in the pacific theater during WW II.

Posted by Kevin Murphy at November 16, 2006 12:03 PM | History