The Battle of the Atlantic

Atlantic U-boat campaign of World War I

Allied losses 8 million tons of shipping, over 4,000 ships, German losses 178 U-boats, 5,000 men.

Initially the U-boat campaign was directed against the British Grand Fleet. Later U-boat fleet action was extended to include action against the trade routes of the Allied powers.

This campaign was highly destructive, and resulted in the loss of nearly half of Britain’s merchant marine fleet during the course of the war.

To counter the German submarines, the Allies moved shipping into convoys guarded by destroyers, blockades such as the Dover Barrage and minefields were laid, and aircraft patrols monitored the U-boat bases.

The U-boat campaign was not able to cut off supplies before the US entered the war in 1917 and in later 1918, the U-boat bases were abandoned in the face of the Allied advance.

1914: Initial campaign

On 6 August 1914, two days after Britain had declared war on Germany, ten U-boats sailed from their base in Heligoland to attack Royal Navy warships in the North Sea in the first submarine war patrols in history.

On the 8th August, off Fair Isle, U-15 sighted three British battleships on manoeuvres and fired a torpedo. This failed to hit, and succeeded only in putting the battleships on their guard. At dawn the next morning, the 1st Light Cruiser Squadron, which was screening the battleships, came into contact with the U-boats. HMS Birmingham sighted U-15, which was lying on the surface. Birmingham immediately altered course and rammed U-15 just behind her conning tower. The submarine was cut in two and sank with all hands.

On 12 August, seven U-boats returned to Heligoland; U-13 was also missing, and it was thought she had been mined.
While the operation was a failure, it caused the Royal Navy some uneasiness, disproving earlier estimates as to U-boats’ radius of action and leaving the security of the Grand Fleet’s unprotected anchorage at Scapa Flow open to question.

On the other hand, the ease with which U-15 had been destroyed by Birmingham encouraged the false belief that submarines were no great danger to surface warships.

First successes

U-21 made history on 5th September 1914, when it torpedoed the Royal Navy light cruiser HMS Pathfinder.

The U-boat had ventured into the Firth of Forth, as far as the Carlingnose Battery beneath the Forth Bridge. At one point the periscope was spotted and the battery opened fire but without success.

Overnight it withdrew from the Forth, patrolling the coast from the Isle of May southwards.

On the morning of 5 September, it observed HMS Pathfinder followed by elements of the 8th Destroyer Flotilla. At midday, the destroyers altered course back towards the Isle of May while Pathfinder continued her patrol. Off St Abbs head, U-boat launched a torpedo attack. The cruiser’s magazine exploded, and the ship sank in four minutes, taking 259 of her crew with her. It was the first combat victory of the modern submarine.

The German U-boats were to get even luckier on 22 September, when U-9 encountered three obsolete Royal Navy armoured cruisers, HMS Aboukir, HMS Cressy, and HMS Hogue.. U-9 sent one torpedo into Aboukir. The captains of Hogue and Cressy assumed Aboukir had struck a mine and came up to assist. U-9 put two torpedoes into Hogue, and then hit Cressy with two more torpedoes as the cruiser tried to flee. The three cruisers sank in less than an hour, killing 1,460 British sailors.

Three weeks later, on 15 October, U-9 also sank the old cruiser HMS Hawke, and the crew of U-9 became national heroes.
The sinkings caused alarm within the British Admiralty, which was increasingly nervous about the security of the Scapa Flow anchorage, and the fleet was sent to ports in Ireland and the west coast of Scotland until adequate defenses were installed at Scapa Flow.
This, in a sense, was a more significant victory than sinking a few old cruisers; the world’s most powerful fleet had been forced to abandon its home base.

The last success of the year came on 31 December. U-24 sighted the British battleship HMS Formidable on manoeuvres in the Channel and torpedoed her. Formidable sank with the loss of 547 of her crew.

1915: War on commerce – First attacks on merchant ships

The first attacks on merchant ships had started in October 1914. On 20 October SS Glitra became the first British merchant vessel to be sunk by a German submarine in World War I. Glitra, bound from Grangemouth to Stavanger, Norway, was stopped and searched by U-17. The operation was performed broadly in accordance with the “cruiser rules”, the crew being ordered into the lifeboats before Glitra was sunk by having her seacocks opened. It was the first time in history a submarine sank a merchant ship.

Less than a week later, on 26 October, U-24 became the first submarine to attack an unarmed merchant ship without warning, when she torpedoed the steamship Admiral Ganteaume, with 2,500 Belgian refugees aboard. Although the ship did not sink, and was towed into Boulogne, 40 lives were lost, mainly due to panic. The U-boat’s commander, claimed he had mistaken her for a troop transport.

On 30 January 1915, U-20,, torpedoed and sank the steamers SS Ikaria, SS Tokomaru, and SS Oriole without warning, and on 1 February fired a torpedo at, but missed, the hospital ship Asturias, despite her being clearly identifiable as a hospital ship by her white paintwork with green bands and red crosses.

Unrestricted submarine warfare

Britons believed before the war that the United Kingdom would starve without North American food.
On 4 February 1915 the first unrestricted campaign against Allied trade was started.

The U-boat had several deficiencies for a commerce raider; its low speed, even on the surface, made it scarcely faster than many merchant ships, while its light gun armament was inadequate against larger vessels. To use the U-boat’s chief weapon, the attack without warning, using torpedoes, meant abandoning the stop-and-search required to avoid harming neutrals.

In the first month 29 ships totalling 89,517 tons were sunk, a pace of destruction which was maintained throughout the summer. As the sinkings increased, so too did the number of politically damaging incidents. On 19 February 1915 U-8 torpedoed Belridge, a neutral tanker travelling between two neutral ports; in March 1915 U-boats sank a Swedish and a Dutch freighter; in April two Greek vessels.

In March 1915 Falaba was sunk, with the loss of one American life, and in April 1915 Harpalyce. On 7 May 1915, U-20 sank RMS Lusitania with the loss of 1,198 lives, 128 of them American citizens.

These incidents caused outrage amongst neutrals and the scope of the unrestricted campaign was scaled back in September 1915 to lessen the risk of those nations entering the war against Germany.

British countermeasures were largely ineffective. The most effective defensive measures proved to be advising merchantmen to turn towards the U-boat and attempt to ram, forcing it to submerge. Over half of all attacks on merchant ships by U-boats were defeated in this way.
However this response freed the U-boat to attack without warning.

Another option was arming ships for self-defence, which, according to the Germans, put them outside the protection of the cruiser rules.
Another option was to arm and man decoy ships with hidden guns, the so-called Q-ship. Granton Harbour was a Q-ship base.

A variant on the idea was to equip small vessels with a submarine escort. In 1915, three U-boats were sunk by Q-ships, and two more by submarines accompanying trawlers. In June 1915 U-40 was sunk by HMS C24 while attacking Taranaki, and in July 19156 U-23 was sunk by C-27 attacking Princess Louise. U-36 was sunk in July 1915 by the Q-ship Prince Charles, and in August and September 1915 U-27 and U-41 were sunk by Q-ship Baralong.

In all, 16 U-boats were destroyed during this phase of the campaign, while they themselves sank 370 ships totalling 750,000 tons

1916: In support of the High Seas fleet

In 1916 the German Navy returned to a strategy of using the U-boats to erode the Grand Fleet’s numerical superiority by staging a series of operations designed to lure the Grand Fleet into a U-boat trap. Due to the U-boats’ poor speed compared to the main battle fleet these operations required U-boat patrol lines to be set up, while the High Seas fleet manoeuvred to draw the Grand Fleet to them.

Several of these operations were staged, in March and April 1916, but with no success. Ironically, the major fleet action which did take place, the Battle of Jutland, in May 1916, saw no U-boat involvement at all; the fleets met and engaged largely by chance, and there were no U-boat patrols anywhere near the battle area. A further series of operations, in August and October 1916, were similarly unsuccesful, and the strategy was abandoned in favour of resuming commerce warfare.

1917: Resumption of unrestricted warfare

In 1917 Germany decided to resume full unrestricted submarine warfare. It was expected to bring America into the war, but the Germans gambled that they could defeat Britain by this means before the US could mobilize. German planners estimated that if the sunk tonnage were to exceed 600,000 tons per month, Britain would be forced to sue for peace after five to six months.

In February 1917 U-boats sank over 414,000 tons, in March 1817 500,000 tons, and in April 1917 over 600,000 tons, the highest total sinking of the war. This, however was the high point.

1917: convoys

In May 1917, the first convoys were introduced, and were immediately successful. Overall losses started to fall; losses to ships in convoy fell dramatically. In the three months following their introduction, on the Atlantic, North Sea, and Scandinavian routes, of 8,894 ships convoyed just 27 were lost to U-boats. By comparison 356 were lost sailing independently.

As shipping losses fell, U-boat losses rose. During the period May to July 1917, 15 U-boats were destroyed in the waters around Britain, compared to 9 the previous quarter, and 4 for the quarter before the campaign was renewed.

As the campaign became more intense, it also became more brutal. 1917 saw a series of attacks on hospital ships, which generally sailed fully lit, to show their non-combatant status.

In January 1917, HMHS Rewa was sunk,in March 1917, HMHS Gloucester Castle, and in June 1917, HMHS Llandovery Castle.

As U-boats became more wary, encounters with Q-ships also became more intense. In February 1917 U-83 was sunk by HMS Farnborough, but only after her captain, allowed her to be torpedoed in order to get close enough to engage. In March 1917 Privet sank U-85 in a 40-minute gun battle, but herself sank before reaching harbour.

In April 1917 Heather was attacked by U-52 and was badly damaged; the U-boat escaped unscathed. And a few days later Tulip was sunk by U-62 whose captain was suspicious of her appearance.

1918: final year

The convoy system was effective in reducing allied shipping losses, while better weapons and tactics made the escorts more successful at intercepting and attacking U-boats. Shipping losses in Atlantic waters were 98 ships (just over 170,000 tons) in January 1918; after a rise in February 1918they fell again, and did not rise above that level for the rest of the war.

In January 1918, 6 U-boats were destroyed; this became the average monthly loss for the year.

The Allies continued to try to block access through the Straits of Dover, with the Dover Barrage. Until November 1917 it was ineffective; up to then just 2 U-boats had been destroyed by the Barrage force, and the Barrage itself had been a magnet for surface raids.

After major improvement in the winter of 1917 it became more effective; in the four-month period after mid-December seven U-boats were destroyed trying to transit the area, and by February 2018 the High Seas Flotilla boats had abandoned the route in favour of sailing round the north coat of Scotland, with a consequent loss of effectiveness. The Flanders boats still tried to use the Channel route, but continued to suffer losses, and after March 1918 switched their operations to Britain’s east coast.

Other measures, particularly against the Flanders flotilla, were the raids on Zeebrugge and Ostend, an attempt to blockade access to the sea. These were largely unsuccessful; the Flanders boats were able to maintain access throughout this period.

During the summer of 1918, the extension of the convoy system and effectiveness of the escorts made the east coast of Britain as dangerous for the U-boats as the Channel had become. In this period, the Flanders flotilla lost a third of its boats, and in the autumn, losses were at 40%. In October 1918, with the German army in full retreat, the Flanders flotilla was forced to abandon its base at Bruges before it was overrun. A number of boats were scuttled there, while the remainder, just 10 boats, returned to bases in Germany.

In the summer of 1918, further steps were taken to reduce the effectiveness of the High Seas Flotillas. In 1918 the Allies, particularly the Americans, undertook to create a Mine Barrage across the North Sea, to block U-boat access to the Western Approaches by the north-about route. This huge undertaking involved laying and maintaining minefields and patrols in deep waters over a distance of 300 nautical miles (556 kilometers). The North Sea Mine Barrage saw the laying of over 70,000 mines, mostly by the United States Navy, during the summer of 1918. From September to November 1918 6 U-boats were sunk by this measure.
On 11 November 1918, World War I ended.

After the Armistice, the remaining U-boats joined the High Seas Fleet in surrender, and were interned at Harwich.