The attack on convoy HX 72

On the night of 21/22 September 1940, several hundred miles west of Ireland, the German submarine U-100 slipped on the surface between the columns of convoy HX 72 and in about four hours sank seven of its ships. Her commander, Kapitänleutnant Joachim Schepke, thus completed an attack begun a day earlier by Otto Kretschmer in U-99. When, on the morning of 22 September, the remaining ships scattered and each made its own way to port, the convoy had lost eleven ships totalling 72,727 GRT, and two more had been damaged. The Germans did not lose a single boat.

Under this date war chronologies usually record only that U-boats inflicted heavy losses on convoys in the Atlantic. That was indeed so: the second half of September 1940 was one of the worst periods of the entire war for British shipping, and HX 72 was the most painful, though not the only, blow of those weeks.

“The happy time”

In the summer of 1940 the situation in the Atlantic shifted in Germany’s favour. After the Armistice of Compiègne the U-boats gained bases on the Bay of Biscay: from July they put into Lorient, and later also into Brest and Saint-Nazaire, which shortened their passage to the hunting grounds by hundreds of miles and lengthened their time on patrol. The Italians joined the war on the ocean from their new base at Bordeaux, and on 17 August Berlin proclaimed a total blockade of the British Isles – in practice a declaration that any ship in the waters around Britain would be sunk without warning.

The British, meanwhile, had too few escort vessels. Many destroyers had been sunk or damaged off Narvik and Dunkirk, and the Admiralty kept those that remained in ports on the east and south coasts in case of a German invasion. Few went to the Atlantic. On the open ocean convoys from Canada were usually protected by only a single armed merchant cruiser, an armed passenger liner that could defend a convoy against a surface raider but not against a submarine. The anti-submarine escort waited only on the approaches to the British Isles. The new Flower-class corvettes were only just entering service, and the fifty old American destroyers from the destroyers-for-bases deal began to be taken over at Halifax in September and took many months to make ready for service.

The Germans had few boats in the Atlantic at this time, usually a dozen or so at once, but their commanders had learnt to exploit the weakness of the escorts. Instead of attacking submerged by day, they slipped into the convoy formation on the surface at night. A surfaced submarine, with the low silhouette of its conning tower, was almost invisible in the dark, and British ASDIC detected only submerged boats. The escorts did not yet have radar. The U-boat crews called these months “the happy time” (die glückliche Zeit). According to figures compiled by uboat.net, in September 1940 submarines sank 57 ships totalling more than 285,000 GRT, roughly as much as in August.

September on the convoy routes

HX 72 was not the month’s first victim. At the beginning of September several U-boats attacked the slow convoy SC 2 from Canada; Günther Prien sank several of its ships and used up most of his torpedoes. On 15 September U-48 under Kapitänleutnant Heinrich Bleichrodt attacked convoy SC 3 and sank not only two merchant ships but also its escorting sloop, HMS Dundee. Kretschmer added two more ships, and by 18 September the convoy had lost six vessels, counting the escort.

The most tragic attack had come five days earlier. Late in the evening of 17 September the same U-48 torpedoed, west of the islet of Rockall, the liner City of Benares, flagship of the commodore of convoy OB 213, bound from Liverpool to America. The escort had left the convoy earlier that day, and the sea was rough, so the lifeboats capsized or were swamped by the waves. Of about 406 people on board, about 260 died. The ship was carrying 90 children being sent to Canada under the government’s overseas evacuation scheme run by the Children’s Overseas Reception Board (CORB). Seventy-seven of them died. The next day the destroyer HMS Hurricane picked up 105 survivors, and one of the lifeboats – carrying, among others, six boys and their escort Mary Cornish – was spotted after eight days adrift by a Short Sunderland flying boat, and its survivors were taken aboard by the destroyer HMS Anthony. According to post-war accounts, the German submariners did not know that the ship was carrying children.

The sinking of the City of Benares shocked Britain. A few weeks earlier, on the night of 30/31 August, the Dutch liner Volendam had been torpedoed, but on that occasion all the children had been saved. Now, in view of public feeling and the reluctance of Winston Churchill, who had never favoured the scheme, the government stopped sending children overseas. By then CORB had evacuated about 2,600 children, mainly to Canada, Australia, South Africa and New Zealand, although more than 200,000 had been registered. From then on children from the cities bombed in the Blitz were evacuated only to the British countryside.

The convoy from Halifax

HX 72 left Halifax, Nova Scotia, on 9 September 1940, bound for Liverpool. According to the records it consisted of 43 ships, including groups joining from Sydney on Cape Breton Island and from Bermuda, carrying what Britain needed to wage war: oil, steel, ore, timber, grain and food. Like the first HX convoy a year earlier, it was led out of port by Canadian warships, and on the ocean it was accompanied only by the armed merchant cruiser HMS Jervis Bay. On the evening of 20 September (according to some records not until the following day) Jervis Bay detached to take over a westbound convoy, and the British escort from home ports had not yet arrived. For a dozen or more hours HX 72 sailed through the most dangerous waters of the ocean without any protection.

The convoy was sighted on 20 September by Prien. His U-47 was then serving as a weather boat, sending weather reports to headquarters, and after the attack on SC 2 had almost no torpedoes left. He could, however, shadow the ships and report their position. The commander of the U-boat arm, Karl Dönitz, a vice-admiral since 1 September, directed the boats that were nearby onto the convoy from his headquarters in occupied France: U-99, U-48, U-100, U-65, U-43, U-32 and several others. It was one of the first attacks in which the tactic later known as the “wolf pack” was used successfully: one boat kept contact while headquarters brought the others onto the convoy.

Three nights of attacks

The first to strike was Kretschmer, then the most successful U-boat commander, who by all accounts followed the rule “one torpedo, one ship” and fired at close range from within the convoy formation. On the night of 20/21 September he sank the large tanker Invershannon (9,154 GRT) and the steamer Baron Blythswood (3,668 GRT). The latter, loaded with iron ore, went down in a matter of seconds, and almost her entire crew died. The Elmbank, torpedoed by Kretschmer, stayed afloat, and on 21 September she was finished off by gunfire from U-99 and Prien’s U-47, who in this way, despite having no torpedoes, claimed a share in the attack. The same day Bleichrodt’s U-48 sank the Blairangus and damaged the Broompark.

On the afternoon of 21 September the local escort finally reached the convoy: the sloop HMS Lowestoft, from which Commander Knapp directed it, the destroyer HMS Shikari and three corvettes, La Malouine, Calendula and Heartsease. Two more destroyers joined the next day. These ships could not, however, prevent what happened that night. Schepke, on the surface, attacked even before moonrise and within a few minutes hit three ships: the Canonesa, the tanker Torinia and the Dalcairn. Just after midnight he struck again, sinking the Empire Airman, the Scholar and the tanker Frederick S. Fales, and towards dawn on 22 September the Norwegian ship Simla. With his last torpedo he tried to hit the Putney Hill as well, but missed, and the ship drove him off with a few rounds from her gun. In all, seven ships of about 50,000 GRT. Also on 22 September Hans Jenisch’s U-32 damaged the Collegian. The escort, which could not see the boats on the surface, fired at them blindly and failed to sink or even seriously damage any of them.

The death tolls given in the sources differ: adding up the figures for individual ships in English-language records gives 113 seamen killed, while other studies give fewer confirmed victims. For that night Schepke received the Knight’s Cross on 24 September, and German propaganda turned him, Kretschmer and Prien into national heroes.

In the same days, on 20 and 21 September, the small submarine U-138 under Wolfgang Lüth, on her first patrol, hit four ships in the westbound convoy OB 216. Within a few days, then, more than a dozen ships went down in the north-western approaches to the British Isles.

Place in the war

HX 72 showed that with weak escorts and night attacks on the surface even a handful of submarines could shatter a large convoy. Dönitz concluded that group tactics worked and in October applied them on a larger scale: the slow convoy SC 7 lost 20 of its 35 ships, and immediately afterwards the fast HX 79 lost one ship in four, both without German losses. The British responded by strengthening the escorts once the threat of invasion had passed, forming permanent escort groups trained to work together, moving escort and air bases forward to Iceland and Northern Ireland, and, the following year, with radar on ships and aircraft and the breaking of German naval ciphers.

The heroes of the September attacks did not survive the following spring at sea. Prien was lost with U-47 in March 1941, in unknown circumstances. Ten days later, on 17 March 1941, during an attack on convoy HX 112, the destroyer HMS Vanoc rammed U-100, and Schepke was killed on the bridge. The same night U-99 was sunk by the destroyer HMS Walker, and Kretschmer was taken prisoner. That marked the end of “the happy time” in the first phase of the Battle of the Atlantic. September 1940 nevertheless remained a symbol of the moment when Britain, defending itself in the air over London, came close to losing the war on the ocean on which its survival depended.