The battle for convoys HX 229 and SC 122

On 17 March 1943, in the middle of the North Atlantic, hundreds of miles from the nearest airfields, the largest convoy battle of the Second World War was under way. Three German wolf packs, some forty submarines in all, attacked two convoys sailing from New York to Britain: the faster HX 229 and the slower SC 122. Over four days, from the night of 16–17 March to 19 March, the U-boats sank 22 merchant ships totalling some 146,000 gross register tons. The Germans lost one submarine. German radio proclaimed “the greatest convoy battle of all time”, and for the first time in the war the British Admiralty wondered whether the convoy system, on which the whole defence of shipping rested, still worked at all.

The worst day was 17 March itself: in the space of twenty-four hours the two convoys lost more than a dozen ships. The battle showed that the middle of the ocean, beyond the reach of land-based aircraft and with too few escort vessels, still belonged to the U-boats. At the same time it proved to be the last great victory of the German submarine fleet. Two months later its offensive in the North Atlantic collapsed.

War on the convoy routes

The Battle of the Atlantic had been going on since the first day of the war. Britain, dependent on food, fuel, raw materials and arms shipped from across the ocean, gathered its ships into convoys protected by destroyers, corvettes and frigates. The Germans responded with wolf pack tactics, devised before the war by the commander of the U-boat arm, Karl Dönitz: a dozen or more submarines strung out in a patrol line waited for a convoy to be sighted, then converged on it and attacked at night on the surface, where a U-boat was faster than when submerged and harder to detect by sonar.

After the United States entered the war, Dönitz spent six months reaping easy pickings off the American coast, until the Americans introduced convoys there and forced him to withdraw his boats in the summer of 1942. From then on the main weight of the fighting returned to the North Atlantic. In the autumn of 1942 the wolf packs were mauling convoys in the zone that aircraft could not reach, as in the battle for convoy ON 127 in September. On the Arctic route, the fate of convoy PQ 17 had shown how tragically the scattering of a convoy could end.

On 30 January 1943 Hitler appointed Dönitz Grand Admiral and Commander-in-Chief of the Kriegsmarine in place of Erich Raeder. Dönitz kept direct command of the submarines and staked everything on them. In the spring of 1943 he had more of them than ever before: over four hundred in service, of which about a hundred were at sea in the Atlantic at any one time in March. On the Allied side, the Casablanca Conference in January had declared the defeat of the U-boats the first condition of all further plans, from the invasion of Europe to the bombing of Germany.

The gap in mid-ocean

The most dangerous stretch of the convoy route was the so-called air gap (also known as the Greenland gap, or in sailors’ slang the Black Pit), a belt of ocean south of Greenland, roughly 600 miles wide, which patrol aircraft from Newfoundland, Iceland and Britain could not reach. An aircraft over a convoy forced the U-boats to dive, and a submerged boat was slow and lost contact with the ships. Without air cover a wolf pack could overtake a convoy on the surface by day and take up position for a night attack. The gap could be closed by very long range (VLR) aircraft, above all converted Liberators, but at the beginning of 1943 RAF Coastal Command had only a dozen or so of them, in a single squadron. Liberators were also wanted by Bomber Command and by the Americans in the Pacific, and the dispute over their allocation had dragged on for months.

There was also a shortage of ships. The ocean escort – the groups of destroyers, corvettes and frigates that took over a convoy off Newfoundland and shepherded it across the ocean – usually numbered between five and eight vessels. Many warships had been absorbed by the landings in North Africa and the Gibraltar convoys, while the new escort carriers and the support groups being formed by the Commander-in-Chief Western Approaches, Admiral Max Horton, were only just entering service. From 1 to 12 March the Allied Atlantic Convoy Conference met in Washington and handed responsibility for the North Atlantic convoys to the British and Canadians, but its decisions were not due to take effect until the spring.

The cipher war

The convoy battles were also fought in intelligence offices. The German navy’s radio monitoring and cryptanalysis service, the B-Dienst, was at that time reading British Naval Cypher No. 3, used for communications with the Atlantic convoys. Thanks to this Dönitz often knew the convoys’ routes and their orders to change course, sometimes before these had reached the ships themselves.

The Allies had a source of their own. In December 1942, after a ten-month break, the codebreakers at Bletchley Park had again begun breaking “Shark”, the four-rotor Enigma key used by the U-boats in the Atlantic. This allowed the Admiralty to route convoys round the patrol lines. Around 10 March 1943, however, the Germans introduced a new weather codebook, which the British had been using as a source of the plain-text fragments needed to break the key. For several crucial days Bletchley Park was “blinded” once more. Convoys HX 229 and SC 122 thus sailed at a moment when the Germans knew a great deal about them and the British knew little about the U-boats.

Two convoys and three wolf packs

Convoy SC 122, a slow convoy (about 7 knots) of 60 ships, left New York on 5 March. Gales drove some of the ships back to port, and on 13 March, at the start of the ocean passage, the convoy was taken over by the British escort group B5 under Commander Richard C. Boyle: the destroyer HMS Havelock, the American destroyer USS Upshur, a frigate, five corvettes and a rescue trawler. HX 229, the faster convoy, with 40 ships, sailed on 8 March. From 14 March it was escorted by group B4, with only four destroyers and a corvette. It was led by Lieutenant Commander Gordon Luther in HMS Volunteer, because the group’s regular commander was in refit, and Luther was making only his second voyage with these ships. A further 34 ships that could not be fitted into HX 229 sailed separately as HX 229A, on a more northerly route.

Dönitz placed three patrol lines across the convoys’ path: Raubgraf (eight boats, already fresh from fighting convoy HX 228) at the western edge of the gap, Stürmer (eighteen boats) in its middle and Dränger (eleven) further east. Thanks to the B-Dienst he knew about SC 122 as early as 13 March. A gale, however, pushed that convoy ahead and it passed through the Raubgraf area before the line had closed. HX 229, sailing on a similar route, slipped past it unnoticed during the night of 15–16 March.

On the morning of 16 March U-653, returning to base with a defect, stumbled on HX 229 by chance and reported it. Dönitz sent Raubgraf in pursuit, and Stürmer and Dränger westwards, ahead of the convoy. He saw the chance he had been waiting for: an eastbound convoy, full of war cargoes for Europe, with the whole width of the air gap ahead of it.

16–17 March: the darkest day

On the evening of 16 March the Raubgraf boats caught up with HX 229. During the night and early morning of 17 March, in the space of about eight hours, they sank eight ships, among them the Dutch Zaanland and Terkoeli, the British whale factory ship Southern Princess, which was carrying oil and landing craft, and the American freighter Harry Luckenbach, from which none of the nearly 80 men survived, although they were seen on rafts afterwards. The weak B4 escort could not hunt U-boats and rescue survivors at the same time. Whenever ships stopped to pick up men from the water, fresh gaps opened in the convoy’s defences.

That same night, some 120 miles further on, Kapitänleutnant Manfred Kinzel’s U-338 of the Stürmer group detected SC 122 and in a short attack sank three ships, and damaged a fourth, the Fort Cedar Lake, so badly that another U-boat finished her off during the day. On 17 March more Stürmer boats were closing in. During the day HX 229 lost two more ships, including the American William Eustis, which was sunk by her own escort. Liberators of No. 120 Squadron RAF, flying from Northern Ireland at the limit of their range, briefly appeared over the convoys. They forced several U-boats to dive and allowed the escort to beat off the daylight attacks. By the end of 17 March the two convoys had lost more than a dozen ships between them.

18–20 March: the convoys sail together

During the night of 17–18 March only some 70 miles separated the two convoys, and the fighting merged into a single battle. U-338 sank the Panamanian Granville from SC 122, and after midnight U-305 sank two more ships, the Port Auckland and the Zouave. Group B4 lost the destroyer HMS Mansfield, which had to detach from the convoy. On 18 March command of HX 229’s escort was taken over by the newly arrived destroyer HMS Highlander under Commander E. C. L. Day, and the destroyers HMS Vimy and USS Babbitt, together with the US Coast Guard cutter USCGC Ingham, sailed from Iceland to help. In the afternoon U-221 sank two ships from HX 229, including the British Canadian Star, which was also carrying passengers.

From 18 March aircraft circled over the convoys more and more often: Liberators, Fortresses (B-17s) and Sunderland flying boats from Iceland and Northern Ireland. The attacks during the night of 18–19 March were beaten off. The last victims were stragglers: the Matthew Luckenbach from HX 229, which had broken away from the convoy on her own initiative and ran into the U-boats hovering around SC 122, the Greek Carras and the British Clarissa Radcliffe, which went down with all hands. On 19 March a B-17 of No. 206 Squadron RAF sank U-384 with all on board, and aircraft and escorts damaged several other boats. Faced with stiffening resistance, Dönitz concluded that further attacks would cost more than they gained, and on 19–20 March he called off the operation. HX 229, with 27 ships, and SC 122, with 42, reached Liverpool on 23 March. HX 229A crossed the ocean without being attacked, although its ships suffered in an ice field and one sank.

The toll

Some 90 merchant ships, more than a dozen escort vessels and 38 U-boats took part in the battle (not all of them in contact with the convoys at the same time). Twenty-two ships were sunk – 13 from HX 229 and 9 from SC 122 – totalling some 146,000 GRT according to British and German tallies. Some studies give 21 ships, counting stragglers and ships finished off by their own escort differently. According to the most frequently cited estimates, about 360 seamen and passengers died, nearly 250 of them from HX 229. The Germans lost one boat, U-384, and its crew of 47.

German propaganda proclaimed a triumph, and the U-boat commanders’ reports, as usual in the confusion of night attacks, exaggerated the number of ships sunk and their tonnage. In London the mood was grim. A later British Naval Staff review recorded: “The Germans never came so near to disrupting communications between the New World and the Old as in the first twenty days of March 1943.” The same study stated that for a time it had seemed possible to the Admiralty that the convoy could no longer be regarded as an effective system of defence. Had that happened, there was no alternative: ships sailing independently were sunk even more easily.

The worst month

The battle for HX 229 and SC 122 was the culmination of a series of clashes in March 1943. In the first weeks of the month the wolf packs had also attacked convoys SC 121 and HX 228. Of the four eastbound convoys that encountered U-boats, 39 ships were sunk, and over the whole of March the Allies lost more than 80 ships in the Atlantic; across all the world’s seas losses exceeded half a million tons. Such a rate could not be made good even by the mass production of Liberty ships in American yards. British stocks of fuel and food were low at the time, and preparations for the invasion of Europe required hundreds of thousands of American soldiers to be shipped across the ocean.

These figures had another side, however. More than two-thirds of the ships in the two convoys reached their destination, four other eastbound convoys crossed in March without loss, and none of the eight westbound convoys was attacked. The U-boats were also losing more and more boats: nine were sunk in the Atlantic in March, and many others returned to base damaged. The Germans had failed to cut the route across the ocean; they had only inflicted grievous wounds on it.

The turn of the tide

The turning point came sooner than anyone in London expected. In March and April support groups joined the convoy routes – groups not tied to a particular convoy’s escort and able to hunt U-boats to the finish – among them the first escort carriers, the American USS Bogue and the British HMS Biter. Under pressure from Roosevelt and Churchill the patrol squadrons received more VLR Liberators, and by May the air gap had practically been closed. Escort vessels were fitted with new centimetric radar, which the Germans for a long time could not detect, HF/DF radio direction-finders, which located the U-boats’ radio reports, and ahead-throwing depth-charge weapons. Bletchley Park was soon reading Shark again, and in June the British replaced the convoy cipher that the B-Dienst had been reading.

In April the wolf packs achieved little, and in May they were defeated. In the battle for convoy ONS 5 at the turn of April and May the Germans sank 13 ships but lost six boats, and in the attack on SC 130 in mid-May they lost more, including U-954, in which Dönitz’s son Peter was killed. Over the whole of May 1943, later called “Black May” by the Germans, the U-Bootwaffe lost more than forty boats, roughly a quarter of the force operating at sea. On 24 May Dönitz withdrew his boats from the North Atlantic.

Its place in the war

The battle for convoys HX 229 and SC 122 was the largest convoy battle of the Second World War and the last great success of the German submarine fleet. It showed that the outcome of the struggle in the Atlantic was decided not by individual clashes but by the range of aircraft, the number of escort vessels and superiority in the cipher war. Once the Allies had closed the gap in mid-ocean, the wolf packs lost their main advantage.

Historians still argue about how close the Allies came to defeat at sea in the spring of 1943. In the past, under the influence of the Admiralty’s own assessments, March was regarded as the moment when the outcome of the war hung in the balance in the Atlantic. More recent work, such as that of Clay Blair and Werner Rahn, stresses that even in the worst months the overwhelming majority of ships reached their destinations, and that American shipyards were building more tonnage than the U-boats could sink. Whatever the verdict, March 1943 remained the blackest month for the Atlantic convoys, and its victims were above all the merchant seamen – British, American, Dutch, Norwegian, Greek and others – who crossed the ocean with no means of defending themselves. After May 1943 the Atlantic route was safe enough for the troops and equipment for the invasion of Europe to be shipped across the ocean.