Tonnage war

The focus on U-boat successes, the so-called "aces" and their scores, the convoys attacked, and the ships sunk, serves to camouflage the Kriegsmarine's manifold failures. In particular, this was because most of the ships sunk by U-boat were not in convoys, but sailing alone, or having become separated from convoys.

At no time during the campaign were supply lines to Britain interrupted; even during the Bismarck crisis, convoys sailed as usual, although with heavier escorts. In all, during the Atlantic Campaign only 10% of transatlantic convoys that sailed were attacked, and of those attacked only an average of 10% of the ships were lost. Overall, more than 99% of all ships sailing to and from the British Isles during World War II did so successfully.

Despite their efforts, the Axis powers were unable to prevent the build-up of Allied invasion forces for the liberation of Europe. In November 1942, at the height of the Atlantic campaign, the US Navy escorted the Operation Torch invasion fleet 3,000 mi (4,800 km) across the Atlantic without hindrance, or even being detected, in what may be the ultimate example of the Allied practise of evasive routing. In 1943 and 1944 the Allies transported some 3 million American and Allied servicemen across the Atlantic without significant loss.

Unlike the Allies, Germany was never able to mount a comprehensive blockade of Britain. Nor were they able to focus their effort by targeting the most valuable cargoes, the eastbound traffic carrying war materiel. Instead they were reduced to the slow attrition of a tonnage war. To win this, the U-boat arm had to sink 300,000 GRT per month in order to overwhelm Britain's shipbuilding capacity and reduce its merchant marine strength.

In only four out of the first 27 months of the war did Germany achieve this target, while after December 1941, when Britain was joined by the US merchant marine and ship yards the target effectively doubled. As a result, the Axis needed to sink 700,000 GRT per month; as the massive expansion of the US shipbuilding industry took effect this target increased still further. The 700,000 ton target was achieved in only one month, November 1942, while after May 1943 average sinkings dropped to less than one tenth of that figure.

By the end of the war, although the U-boat arm had sunk 6,000 ships totalling 21 million GRT, the Allies had built over 38 million tons of new shipping.^{[citation needed]}

The reason for the misperception that the German blockade came close to success may be found in post-war writings by both German and British authors. Blair attributes the distortion to "propagandists" who "glorified and exaggerated the successes of German submariners", while he believes Allied writers "had their own reasons for exaggerating the peril".^[2]

Dan van der Vat suggests that, unlike the US, or Canada and Britain's other dominions, which were protected by oceanic distances, Britain was at the end of the transatlantic supply route closest to German bases; for Britain it was a lifeline. It is this which led to Churchill's concerns.^[4] Coupled with a series of major convoy battles in the space of a month, it undermined confidence in the convoy system in March 1943, to the point Britain considered abandoning it,^[5][6] not realising the U-boat had already effectively been defeated. These were "over-pessimistic threat assessments", Blair concludes: "At no time did the German U-boat force ever come close to winning the Battle of the Atlantic or bringing on the collapse of Great Britain".^[7]

Mediterranean

The second tonnage war was the Allied campaign against Axis shipping, mostly

There was another tonnage war in the Mediterranean, as Gibraltar convoys battled against Axis submarines and aircraft to deliver supplies and equipment to Malta, which was under siege by air and sea. The deliveries enabled Malta to resist persistent air attacks and take the offensive against Axis convoys.

Pacific

In the early years of the

Despite an awareness that shipping was vital, the Japanese military seriously underestimated the eventual threat from Allied submarines. This overconfidence was reinforced by the ineffectiveness of the early activities of Allied submarines in the Pacific War.^[8] Anti-submarine warfare was accorded a low priority and few warships and aircraft were allocated to protecting merchant shipping.^[9] Japanese destroyers formed the bulk of convoy protection throughout the war, while the Allies recognized earlier the need to use the more economical destroyer escorts for convoys, something the Japanese realized too late. The Japanese had impressive night fighting capabilities and heavy torpedo loadouts, but had deficiencies in sonar and radar compared to other navies.^[10] Moreover, Japanese Naval doctrine in relation to commerce defense was quite poor.^[11]

During the summer of 1943, substantial numbers of

Japanese submarines, despite their technical prowess and numbers, were used for fleet warfare instead of against the Allied merchant marine in the Pacific theater, thus Allied shipping lanes in the Pacific were not disrupted.

In and around

• Naval strategy
• Commerce raiding
• Unrestricted submarine warfare
• Merchant raider

References