Figure 1.--.

"The Germans never came so near to disrupting communications between the New World and the Old as in the first 20 days of March 1943."

-- Royal Navy historian.

The year 1942 began as a series of Allied disasters: the Germans prevailed on the Eastern Front reaching the Volga, in North Africa and in the North Atlantic. And the Japanese in the Pacific seemed almost like supermen--until Midway (June 1942), but this only slowed the Japanese advances. In this dismal picture, here was a sudden miraculous shift. First at Guadalcanal (August 1942). But the big threat was the Germans and then they too suddenly began to crack. First at El Alamein (October 1942). Then Stalingrad and French North Africa (November 1942). By the beginning of 1943, the strategic picture had been suddenly turned on its head. The Axis powers had not only been stopped, but were losing ground and absorbing mountainous, unsustainable losses. In addition, the strategic bombing campaign had finally begun to have an impact, bringing the war home to the Germans. The one campaign that continued going well for the Germans was the U-boat campaign in the North Atlantic. The Germans not only were still sinking large numbers of Allied cargo vessels, but were increasing U-boat construction at a much faster rate than he Allies were destroying U-boats. The one problem Dönitz had earlier was he U-boat fleet was too small to have an impact. They were sinking ships, but Britain had a huge merchant marine. By 1943 Dönitz finally had a U-boat force capable of maintaining the the 100 U-boats at sea that he wanted. And Hitler had replaced Adm. Raeder with him as commander of the Kriegsmarine. The Royal Navy was beginning to question the viability of convoying. The final show down came in the Black Gap (May 1943). What was at stake was supplying Britain, but also the ability to build up the forces in Britain needed for the all-important cross-channel invasion--baisically the entire Western war effort. This was primrily based on American industrial power. Without defanging the German U-boat campaign, America had no way of projecting its immense power.

U-boat Construcion

Tipping Point (January-February 1943)

The primary tactic of the Royal Navy with its limited escorts was to avoid the U-boats. And with the small number of U-boats available to Dönitz, this and the convoy system proved the most effective tactics. The Submarine Tracking System was this the heart of the Royal Navy's effort. Because Shark, the Enigma key used by Dönitz proved so impenetrable, until 1943, they had to rely omly on radio directional operations to locate the U-boats and redirect the convoys. Dönitz was flooding the Atlantic with U-boats, finally having obtained Hitler's support for a mssive U-boat building program. (After Barbarossa failed before Moscow and declaring war on America, it was obvious that unless the sea lanes could be cut, Germany would be caught in the same two front war that had spelled disaater in World War I.) And with the increasing number of U-boats, it became increasingly difficilt to find safe routes for redirectiong the convoys. It is at this time that several factors came together to tip the ballance to the Allies. The Bletchey Park code breakers finally began to break into Shark. This frustrated Dönitz because despite the number of U-boats deployed (40 on patrol in the vital North Atlantic convoy lanes), theu were not finding convoys and sinking ships. And he did not know why. And at the same time the Germans began having difficulty with British Naval Cipher 3. This helped with redirecting the convoys, but given the number of U-boats redirection was no longer such an effective method as it once was. Now the Royal Navy and the U.S. Navy would have to shoot it out with the U-boats and fight the convoys through. And here breaking into Shark was part of several Allied effortsthat came together at the same time. This included a range of technical advamnces, increased escots (from American and Canadian shipyards as well as the soon to be relaesed shiops from victory in North Africa) and the all imortant extension of air cover to include the mid-Atlantic air gap. The battle during January-February swung back and forth with the Germans suceeded in savaging several convoys. Often decrypts saved or failed to save convoys by only a matter of minutes.

Continued Sinkings (Early 1943)

German U-boats in early 1943 continued sinking substantial numbers of merchant vessels, although not as many a Dönitz had anticipated with his expanded U-boat fkleet. The British food supply in early 1943 was down to a few months. The U-boats sank about 100 merchant vessels in 1943, mostly in the first half of the year. That was a rate that could not be replaced even by the Liberty Ships coming out of the new shipyrds. U-boat sinkings were also increasing. A major engagement was fought im March involving 80 merchants, 20 escort vessels, 44 U-bots and numerous aircraft. The U-boats achieved numerous kills in March. Royal Naval reports indicate that in March the U-boats came the closest to cutting Britain's Atlantic life lines. The engagements in the North Atlantic were, hioever, no longer one-sided. American shipyards were mot jut building Liberty Ships, they were also steadily expnding production of escort ships. In particular, three new escort carriers were delivered (April). The Allied sank 15 U-boats in April 1943. More than in the past, but still not enough to deter the Germans. After the German defeats in the East amd North Africa, the North Atantic comtinued to be the onle paves where successes were still being achieved.

Black May (May 1943)

The war at sea turned a few months later--May 1943. German intellience learned of a major 43-ship convoy from Britain to America, ONS-5, with only six escorts. It departed (April 22). At first it had air cover. Dönitz ordered a massive 40-U-boat force of two Wolf Pack to form in th mid-Atlantic air gap. It was the largest U-boat force ever committed. They were to attack in force to demonstate the power of his expanding fleet. Dönitz radioed, "Fight with everything you got. Strike the eneny dead." It would be a 4-day knock-down drag-out fight. Horton informed the convoy that they were surrounded by U-boats, but they were on their owm in the mid-Atlantic air gap (May 4). The Wolf Pack sank seven merchantmen on the first day. The next day the U-boats pressed the attack. Allied escorts with little air cover engaged the Wolf Packs. ONS-5 would lose 12 merchant ships. But in the single engagement 6 U-boats were sunk, 5 wrecked, and 12 damaged. In just one battle they did far more damage to the U-boat fleet than in any other month of the war. That totaled nearly a third of the U-boats on patrol in the convoy lanes. It was a stunning reversal and notably it was achieved by only 6 escorts with no air support. And further German losses cointinued during the rest of the month. Dönitz formed another large Wolf Pack to attack a convoy. This time the resukt was even more disterous for the Gemans. They lost five U-boats and did not sink a single merchantman. During May the building Allied naval strength in the Atlantic and widening technical superiority succeeded in sinking 41 U-boats and damaging 37 others. Among the lost crews were Dönitz's younger son Peter on U-954. (His older son Klaus would be killed later in the War.) and even worse for Dönitz, the Allies were in the process of closing the mid-Atlantic air gap as well as deoloying improved radars and ASW weaponry.

Created: 2:17 AM 4/3/2026
Last updated: 2:17 AM 4/3/2026