Germany widens the U-boat war

In the twenty-four hours that began on 15 February 1940, German submarines sank six ships. All of them sailed under neutral flags. During the night U-50 torpedoed the Danish steamer Maryland, bound from Brazil to Copenhagen, west of the Hebrides; the ship broke in two and sank in seven minutes with her entire crew of 34. Before dawn U-37 sank the Danish Aase, carrying fruit from Valencia to Bristol, in the Western Approaches to the English Channel; one man survived. In the morning U-26 sent the Norwegian ore carrier Steinstad to the bottom off the west coast of Ireland; in the afternoon U-48 under Kapitänleutnant Herbert Schultze torpedoed the Dutch tanker Den Haag some 150 miles west of Ushant; and late in the evening and just after midnight U-14 sank two Danish ships, Rhone and Sleipner, in the North Sea east of Scotland. In a single day more than a hundred seamen from countries taking no part in the war lost their lives.

Many chronologies record under this date that Adolf Hitler ordered unrestricted submarine warfare. The available German naval documents – the records of Grand Admiral Erich Raeder’s conferences with Hitler, the war diary of the U-boat command and the chronicles of the war at sea based on them – know of no order issued on 15 February. Against British and French ships the U-boats had been waging unrestricted submarine warfare since October 1939. Nor, by mid-February 1940, was it anything new for neutral ships to be sunk without warning. What was changing was something else: since January the areas in which this was permitted had been growing, and sinkings of neutral ships had become an everyday occurrence. The widening of the submarine war was thus a process, not a single order.

From prize rules to zones

In the autumn of 1939 Karl Dönitz and Raeder had stripped away step by step the restrictions that the prize regulations imposed on submarines. Under these rules a merchant ship could be sunk only after it had been stopped, its cargo inspected and the safety of its crew ensured. By mid-October this protection no longer applied to enemy ships. Neutral ships still enjoyed it, at least on paper, because sinking them on a large scale risked conflict with states that mattered to Germany, above all the United States.

The solution the navy worked out around the turn of the year was zones. On 30 December 1939 Hitler agreed that within the area closed to American ships by the Neutrality Act, Greek ships might be sunk without warning, and that where a sinking could be attributed to mines – for example in the Bristol Channel – all ships might be. The implementing directive of the Wehrmacht High Command stipulated that the attack was to be carried out unobserved and that, in the event of protests, the sinking must be deniable. According to the findings of the International Military Tribunal at Nuremberg, on 1 January 1940 the U-boat command passed this on to the boats as an order. On 6 January “immediate unrestricted use of weapons against all ships” was ordered in a designated area of the North Sea, and on 18 January permission was given to sink without warning all ships in waters off the enemy coast where the action of mines could be simulated.

The January widening

The next step was taken at the end of January. On 26 January 1940 Raeder put to Hitler a proposal to enlarge the zones in which neutral ships, too, could be sunk without warning, with the exception of those of friendly states. Hitler agreed. The zone off the north-east coast of Scotland was pushed east to the second meridian of east longitude, the zone in the Bristol Channel was extended westward, and a new one was drawn along the east coast of England, from Dover to Flamborough Head. According to the chronology of the war at sea by Jürgen Rohwer and Gerhard Hümmelchen, attacks were to be covert, so that a sinking would look like a mine strike, and only American, Japanese, Italian, Spanish and Soviet ships were to be spared. On 27 January Dönitz noted in his war diary that the naval war staff had enlarged zones “A” and “B” and designated a new zone “C” in the North Sea.

The same records show how the system worked. In its February lists of successes, the U-boat command recorded, alongside ships identified by name and flag, entries described only as “steamer in zone A” or “steamer in zone B”, with no name and no nationality. Ships sunk in the zones were not officially to have been sunk by U-boats.

Outside the zones prize law formally still applied, but the line was blurring, since darkened neutral ships often could not be identified. The fate of the ships sunk on 15 February shows both sides of this practice. The commander of U-26 shadowed the Steinstad all night because he had made out the Norwegian flag and wanted to stop the ship at dawn in accordance with the prize rules. The ore carrier ignored warning shots, and after the third she turned towards the submarine. Only when shells began to fall closer did the crew take to two lifeboats, whereupon the U-boat torpedoed the ship, which sank in a few seconds. The lifeboat carrying the master and twelve seamen was never found. The Maryland, Aase and Den Haag were torpedoed without any warning at all. The Sleipner stopped to rescue survivors from the Rhone and sent out a distress call, and a few minutes later was herself hit by a torpedo; the lifeboats lowered before she was struck saved most of her men and some of the Rhone’s survivors.

The worst month for the neutrals

By the end of January 1940, after a decline over the autumn and winter, Germany once again had as many U-boats at sea as at the start of the war. According to the report Raeder made to Hitler on 23 February, about six boats were constantly operating in the Atlantic and eight in the North Sea, and results in the Atlantic were improving patrol by patrol. A post-war US Navy study of anti-submarine warfare judged that the U-boat effort in February was greater than in any earlier period of the war.

The burden of these operations fell largely on neutral shipping. According to the figures compiled by uboat.net, in February 1940 submarines sank 51 ships and warships by torpedo or with mines they had laid themselves, and damaged two. Eighteen of those sunk were British, including a destroyer, and one was French. The other 32 sailed under neutral flags: seven Swedish, seven Norwegian, six Danish, four Dutch, three Estonian, and one each Finnish, Greek, Spanish, Panamanian and Italian. In January, when U-44 and U-22 were sinking Greek and Danish ships, neutrals had already made up the majority of the victims, as the story of the Exmouth and the Tekla showed. In February the proportion was much the same.

Scandinavian ships paid the price for their countries’ inability to do without trade with Britain. In the North Sea the U-boats hunted the shipping between Scotland and Norway, where the British were already running convoys that neutral ships joined. The Germans, too, bore the cost of the war. On 23 February Raeder reported to Hitler that since the start of the war the navy had lost twelve submarines, roughly two a month. Among those lost in February were U-41, sunk on 5 February by the destroyer HMS Antelope, and U-33, sunk on 12 February in the Firth of Clyde; from her survivors the British recovered rotors of the Enigma cipher machine, valuable to the cryptanalysts at Bletchley Park. Then there were the unreliable torpedo pistols: the Maryland and the Rhone, too, were hit only by a second torpedo, because the first exploded prematurely.

Caution towards America

The limits of this policy were set by America. American ships were to remain untouched, and the zones lay within the area that the United States had itself closed to its shipping. It was remembered that in 1917 the declaration of unrestricted submarine warfare had drawn America into the war, and Berlin did not want to hand President Franklin Delano Roosevelt arguments against the isolationists. That is why, this time, Germany announced nothing.

The same caution was evident at the conference of 23 February, attended by the head of the OKW, Wilhelm Keitel, General Alfred Jodl and Hitler’s naval adjutant, Korvettenkapitän Karl-Jesko von Puttkamer. Raeder asked for a further tightening: permission to attack, within the area closed by the Americans, darkened passenger ships showing only navigation lights as well, on the presumption that they were British. He argued that, for want of freighters, the British were using passenger ships to carry goods and troops. Hitler agreed. He refused, however, an operation the navy was very keen on: sending two or three submarines to the Canadian port of Halifax to lay mines and attack shipping. He judged that the psychological effect of such an action in the United States would be too dangerous.

Significance

The February U-boat offensive continued until the end of the month. On 18 February U-23 under Otto Kretschmer sank the destroyer HMS Daring, escorting a convoy from Norway, east of the Orkneys; more than 150 men were killed. On the same day U-53 sank the Spanish steamer Banderas off Cape Finisterre, although Spanish ships were supposed to be spared, and on 29 February U-20 torpedoed the Italian ship Maria Rosa off Lowestoft, having failed to notice her illuminated neutrality markings. In the last days of February British destroyers sank U-53 and U-63. In March the submarines vanished from the Atlantic: Dönitz had to hold them back for the invasion of Norway that Hitler was preparing. In April and May the countries whose ships had been sinking all winter – Norway, Denmark and the Netherlands – themselves fell victim to German aggression.

Germany made no formal declaration until 17 August 1940, when, after the fall of France, it proclaimed a total blockade of the British Isles. Yet by February 1940 sinking neutral ships without warning in declared or secret operational zones was already everyday practice. After the war the Nuremberg tribunal found precisely this practice to be a breach of the London Protocol of 1936 on submarine warfare. For the history of the Battle of the Atlantic something else proved more important. The winter of 1939–1940 showed the merchant fleets of the neutral states that neutrality at sea was no protection against a torpedo, and that sailing alone to a British port was more dangerous than sailing in a British convoy. After April and May 1940 much of the Norwegian, Dutch and Danish merchant fleets passed into Allied service and sailed in convoys until the end of the war.