Isegoria

The “failed” German U-boat campaign in the Atlantic likely cost the Allies 10 times what it cost the Germans, Michel Thomas Poirier says, and the American sub campaign against the Japanese was even more successful:

Based on this rough estimate, the Japanese spent at least 42 times more on Anti-Submarine Warfare and in losses attributed to submarines than the U.S. spent on her Submarine Force. When one considers the fact that the Japanese economy was only 8.9% of the size of the U.S. economy in 1937, the submarine campaign was clearly an extraordinarily cost efficient means to employ U.S. forces against Japan.(96)

We have examined the direct, indirect and second-order effects of the U.S. submarine campaign against Japanese raw material and petroleum imports as well as the effects on four pillars of Japanese power. Fully a year before the end of the war, and before the extensive bombing of mainland Japan, the war against Japanese lines of communication resulted in decisive impact on the Japanese war economy and on the Japanese military logistical system.

We can draw several important lessons on the effectiveness of submarines attacking sea lines of communication based on our study of the two World War II historical cases. First, both these campaigns were directed against vulnerable opponents who required the use of the sea both to import raw materials and to project military forces far from the homeland. A submarine attack on seagoing logistical lines of communication would obviously not be effective against an insular, continental power. Second, both campaigns, including the “failed” German effort, incurred disproportionate costs on the side conducting Anti-Submarine Warfare (ASW). Third, the indirect and second order effects of these campaigns were virtually as important as the direct costs. In fact, the continuing indirect and second order effects played a key role in logistically constraining the Allies in the Atlantic after the allied defeat of the U-boat threat. Finally, in both campaigns, the effects of submarine warfare on an opponent resulted in a substantial reduction of the opponent’s strategic choice and had significant effects on his industrial policy. In the case of the Atlantic campaign, the Allies modified industrial priorities and reduced production of amphibious lift. Lack of logistical and amphibious lift resulted in constrained allied strategic choice for most of the war including a delayed ability to open a second front in France. In the case of Japan, the U.S. submarine campaign substantially reduced Japanese war production, and, ultimately, significantly reduced the Japanese ability to implement their preferred defensive strategy. As a result, the submarine campaign proved itself as an efficient way to wage war against a competitor that must supply its forces over long distances by sea.

It is interesting to contemplate to what degree the United States is vulnerable today to a campaign by a committed regional power or peer competitor against our sea lines of communications. Within the U.S. Navy today, one hears some discussion on the possible impact of submarine attacks against our battle groups, but few consider the impact a campaign against our vulnerable sealift train might have. Since America remains dependent today on sealift to project military power, an opponent might well assess this vulnerability worth exploiting.

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