Atlantic U-Boat Campaign of World War I

The Atlantic U-boat movement of World War I, also known as the "First Battle of the Atlantic" about the World War II campaign of the same name, was a long-running naval battle between German submarines and Allied navies in Atlantic waters, including the seas around the British Isles, the North Sea, and the French coast.

The U-boat campaign was first aimed at the British Grand Fleet. However, the action of the U-boat fleet was later expanded to include action against the Allied nations' commercial routes. This campaign was highly devastating during the war, resulting in over half of Britain's commercial marine fleet. To resist the German submarines, the Allies put their ships in convoys guarded by destroyers, set up blockades and minefields like the Dover Barrage, and had aviation patrols monitor the U-boat sites.

Before the United States arrived the war in 1917, the U-boat campaign could not cut off supplies, and the U-boat bases were abandoned in the face of the Allied assault in late 1918. Nevertheless, the Atlantic U-boat Campaign's tactical triumphs and failures would eventually be used as a set of possible tactics in a similar U-boat battle against the British Empire during World War II.

First Patrols

The German U-boats U-5, U-7, U-8, U-9, U-13, U-14, U-15, U-16, U-17, and U-18 sailed from their base in Heligoland on 6 August 1914, two days after Britain declared war on Germany, to target Royal Navy warships in the North Sea in the first submarine war patrols in history. Between Shetland and Bergen, the U-boats proceeded north, expecting to run across Royal Navy squadrons. However, one of U-9's engines failed on 8 August, forcing her to return to base. U-15 saw the British battleships HMS Ajax, Monarch, and Orion on drills off Fair Isle the same day and fired a torpedo at Monarch. This failed to hit the target and merely served to alert the battleships. The 1st Light Cruiser Regiment, which was screening the battleships, came into contact with the U-boats at daybreak the following day, with HMS Birmingham spotting U-15 lying on the surface. On the U-boat, there were no lookouts and sounds of hammering could be heard, as if her crew was doing repairs. Birmingham abruptly changed course and collided with U-15 just behind her conning tower. The submarine was sunk with all personnel after being cut in half.

Seven U-boats returned to Heligoland on 12 August. U-13 had gone missing as well, and it was suspected that she had been mined. While the operation was a failure, it did raise some concern among Royal Navy officers since it disproved earlier estimates of U-boat range and cast doubt on the security of the Grand Fleet's unguarded anchorage at Scapa Flow. The ease with which Birmingham destroyed U-15, on the other hand, promoted the mistaken idea that submarines posed no significant threat to surface warships.

First Successes

Lieutenant Otto Hersing's U-21 sank the Royal Navy light cruiser HMS Pathfinder on 5 September 1914, making history. The cruiser's magazine blasted, and the ship sank in four minutes, killing 259 people. It was the modern submarine's first combat victory.

On 22 September, the German U-boats would have even better luck. A lookout on the bridge of U-9, led by Lieutenant Otto Weddigen, observed a vessel on the horizon early that morning. Weddigen ordered the submarine to submerge quickly, and the submersible proceeded to investigate. Weddigen discovered three historic Royal Navy armoured cruisers, HMS Aboukir, Cressy, and Hogue, closer. These three ships were not just old, but they were manned mainly by reservists and were visibly vulnerable, so a decision to evacuate them was already making its way up the Admiralty's bureaucracy. Unfortunately, for the ships, the order did not arrive quickly enough. One torpedo was launched into Aboukir by Weddigen. Hogue and Cressy's leaders assumed Aboukir had hit a mine and rushed up to help. As the cruiser attempted to flee, U-9 fired two torpedoes at Hogue, followed by two more at Cressy. In less than an hour, the three cruisers sank, killing 1,460 British sailors.

Weddigen sunk the ageing cruiser HMS Hawke three weeks later, on 15 October, and the men of U-9 became national heroes. Except for Weddigen, who obtained the Iron Cross First Class, everybody received the Iron Cross Second Class. The sinkings alarmed the British Admiralty, which became increasingly concerned about the Scapa Flow harbour's security, and the fleet was dispatched to ports in Ireland and Scotland's west coast until suitable fortifications could be installed. In other ways, losing a few outdated cruisers was a less meaningful triumph; the world's mightiest fleet had been forced to quit its home port.

End of the First Campaign

These worries were justified. On 23 November, U-18 entered Scapa Flow via Hoxa Sound, following a steamer past the boom and quickly approaching the anchorage. On the other hand, the fleet was missing, dispersed in anchorages throughout Scotland's and Ireland's west coasts. A guard boat noticed U-18's periscope as she made her way back out to the open Sea. Dorothy Gray, a trawler, changed course and rammed the periscope, making it useless. The dive plane motor on the U-18 suddenly failed, and the boat was unable to maintain its depth, crashing onto the bottom at one point. Her captain was eventually compelled to surface and surrender command, and all but one of her crew members were picked up by British boats. The year's final success occurred on 31 December. The British battleship HMS Formidable was on manoeuvres in the English Channel when U-24 spotted her and torpedoed her. The Formidable sank, killing 547 of her crew members. The Commander-in-Chief of the Channel Fleet, Adm. Sir Lewis Bayly, was chastised for not taking adequate safeguards during the exercises but was exonerated. Bayly later rose through the ranks of the anti-submarine warfare units at Queenstown, where he excelled.

First Attacks on Merchant Ships

In October 1914, the first strikes against commerce ships began. Glitra was the first British merchant ship to be sunk by a German submarine during World War I on 20 October 1914. U-17, under the leadership of Kapitänleutnant Johannes Feldkirchener, stopped and searched Glitra, which was traveling from Grangemouth to Stavanger, Norway. The crew was ordered into the lifeboats before the Glitra was fallen by having her seacocks opened, and the operation was carried out substantially following cruiser norms. It was the first time a submarine sank a commerce ship in history.

When U-24 attacked the steamship Admiral Ganteaume, carrying 2,500 Belgian refugees, less than a week later, she became the first submarine to strike an unarmed commerce ship without warning. Although the boat did not sink and was brought into Boulogne, 40 people died, mainly due to terror. Rudolf Schneider, the commander of the U-boat, claimed he mistook her for a troop transport. U-20, instructed by Kapitänleutnant Otto Dröscher, torpedoed and sank the steamships Ikaria, Tokomaru, and Oriole without notifying on 30 January 1915, and on 1 February shot a torpedo at, but did miss, the hospital ship Asturias, despite her white-painted surfaces with green bands and red crosses identifying her as a hospital ship.

Unrestricted Submarine Warfare

Before the war, many Britons feared that the United Kingdom would starve if it did not have access to North American food. The first unrestricted operation against Allied trade began on 4 February 1915. For a commercial raider, the U-boat had significant flaws. Its slow speed, especially on the surface, rendered it slower than many commerce ships, and its meagre gun armament left her vulnerable to larger vessels. Moreover, to employ the U-primary boat's armament, torpedoes, without notice, meant preceding the required stop-and-search to avoid hurting neutrals.

The first month saw 29 ships sunk, totalling 89,517 GRT, a rate of destruction that continued throughout the summer. As the number of shipwrecks grew, so did the number of politically detrimental events. U-8 destroyed Belridge, a neutral tanker travelling between two neutral ports, on 19 February. The Falaba was lost in March, killing one American, and the Harpalyce, a Belgian relief ship, was sunk in April. U-20 sunk the RMS Lusitania on 7 May, killing 1,198 people, including 128 Americans. The breadth of the unrestricted campaign was scaled back in September 1915 to reduce the chance of those nations joining the war against Germany due to these episodes, which outraged neutrals.

British retaliation was mainly ineffectual. Recommending merchantmen to turn towards the U-boat and try to ram it, forcing it to sink, proved to be the most effective defensive strategy. This method was used to defeat more than half of all U-boat attacks on cargo ships. However, this response allowed the U-boat to attack without warning. The Great Eastern Railway packet Brussels employed this approach to avoid an attack by U-33 on 20 March 1915. After being seized by the Germans in June 1916, her commander, Charles Fryatt, was shot for this, prompting widespread criticism. Another possibility was to arm ships for self-defence, which the Germans claimed would put them outside the protection of the cruiser rules.

Another possibility was to arm and man Q-ships, which were decoy ships with hidden cannons. Small vessels could be outfitted with a submarine escort as a variation on the concept. Three U-boats were sunk by Q-ships in 1915, while two more were downed by submarines escorting trawlers. U-40 was sunk by HMS C24 while assaulting Taranaki in June, while U-23 was sunk by C-27 while attacking Princess Louise in July. The Q-ship Prince Charles sank U-36 in July, and U-27 and U-41 were sunk by Baralong in August and September, the former in the infamous Baralong Incident. Submerged U-boats, on the other hand, were impossible to detect, and attacks on them were confined to hammering their periscopes and dropping guncotton bombs. The use of nets to catch U-boats was also investigated, as was a destroyer named Starfish equipped with a spar torpedo. During this part of the campaign, 16 U-boats were sunk, and they sank 370 ships with a combined tonnage of 750,000 GRT.

In 1916, the German Navy resumed its use of U-boats to undermine the Grand Fleet's numerical superiority by executing a series of operations to lure the Grand Fleet into a U-boat trap. Due to the U-boats' slow speed compared to the main battle fleet, these actions necessitated the establishment of U-boat patrol lines while the High Seas fleet manoeuvred to attract the Grand Fleet's attention. In March and April 1916, several of these operations were staged, but none were successful. The Fighting of Jutland, which took place in May 1916, had no U-boat involvement; the fleets met and engaged entirely by happenstance, and there were no U-boat patrols anywhere near the battle area. In August and October 1916, a new set of operations were similarly ineffective, and the plan was abandoned in favour of restarting trade warfare.

Germany planned to resume full-fledged submarine warfare in 1917. It was supposed to draw America into the conflict, but the Germans bet that by doing so, they might beat Britain before the Americans could mobilize. If the sunk tonnage exceeded 600,000 tons per month, German planners anticipated Britain would be obliged to sue for peace after five to six months. U-boats sank over 414,000 GRT in the battle zone near Britain in February 1917, accounting for 80% of the total for the month; over 500,000 (90%) in March; and over 600,000 of 860,000 GRT in April, the highest total sinking’s of the war. This, on the other hand, was the pinnacle.

The first convoys were introduced in May, and they were a huge success. Overall losses began to decline, and failures to convoy ships decreased drastically. Only 27 boats were lost to U-boats on the Atlantic, North Sea, and Scandinavian routes three months following their introduction. In comparison, 356 people were lost when sailing alone. U-boat losses increased as shipping losses decreased; from May to July 1917, 15 U-boats were lost in the waters near Britain, compared to 9 the previous quarter and four the quarter before the campaign was revived.

As the campaign progressed, it became increasingly savage. Hospital ships, which sailed fully lit to demonstrate their non-combatant status, were targeted in a series of raids in 1917. U-55 sank the HMHS Rewa in January, U-32 sunk the HMHS Gloucester Castle in March, and U-86 sunk the HMHS Llandovery Castle in June. As U-boats became more careful, Q-ship engagements got more intense. HMS Farnborough sank U-83 in February 1917, but only after Farnborough's captain, Gordon Campbell, allowed her to be torpedoed to approach near enough to engage. Privet sank U-85 in a 40-minute gun engagement in March, but she sank before reaching the harbor. Heather was struck by U-52 in April and was severely damaged; the U-boat was unharmed. Tulip was sunk a few days later by U-62, whose commander was skeptical of her presence.

The convoy system was beneficial in minimizing allied shipping losses, and the escorts were more successful in intercepting and attacking U-boats thanks to better weapons and tactics. In January, 98 ships were lost in Atlantic waters; despite a brief spike in February, they fell again and did not reach above that level for the rest of the conflict. Six U-boats were sunk in the theatre in January, and this became the year's average loss.

With the Dover Barrage, the Allies continued to try to limit access via the Straits of Dover. It was ineffectual until November 1917; the Barrage force had only sunk two U-boats up to that point, and the Barrage itself had been a magnet for surface raids. It became more effective after a significant improvement in the winter of 1917; seven U-boats were destroyed trying to transit the area in the four months after mid-December, and by February, the High Seas Flotilla boats had abandoned the route in favour of sailing north-around around Scotland, resulting in a loss of effectiveness. The Flemish boats attempted to use the passage again but continued to lose ships, and after March, they shifted their operations to the east coast of the United Kingdom.

The raids on Zeebrugge and Ostend, an attempt to limit access to the Sea, were also used against the Flanders flotilla. However, these were primarily ineffective, as the Flanders boats could keep access throughout this time. The first attempt by the Germans to organize a coordinated attack, the progenitor of the wolf-pack, to disrupt Allied convoys occurred in May 1918. Six U-boats sailed in May, with K/L Claus Rücker in command of U-103. U-86 sank one of two ships detached from a convoy in the Channel on 11 May, but U-103 was destroyed the next day in an attack on the troopship RMS Olympic, while British submarine HMS D4 sank UB-72. In the next week, two further convoys and three independents were sunk, although over 100 ships had safely passed through the patrol area of the group.

During the summer, the east coast of Britain became as perilous for U-boats as the Channel had become due to the expansion of the convoy system and the efficacy of the escorts. During this time, the Flanders flotilla lost a third of its boats, with losses reaching 40% in the autumn. The Flanders flotilla was forced to quit its base at Bruges in October, with the German army in full retreat, before it was captured. Several boats were sunk there, while the rest, only ten ships, were returned to German bases.

Steps were also taken throughout the summer to diminish the effectiveness of the High Seas Flotillas. In 1918, the Allies, primarily the United States, decided to build a barrage across the Norwegian Sea to prevent U-boats from using the north-around route to reach the Western Approaches. This massive project entailed constructing and maintaining minefields and patrols in deep waters over a 300-nautical-mile area. During the summer of 1918, the North Sea Mine Barrage saw the placement of almost 70,000 mines, mainly by the US Navy. This measure sank six U-boats between September and November 1918.

U-156 travelled to Massachusetts in July 1918 and participated in the Attack on Orleans for about an hour. This was the first time a foreign power's artillery struck US soil since the Siege of Fort Texas in 1846 and one of only two places in North America to be attacked by the Central Powers. The Battle of Ambos Nogales, which two German spies supposedly led, was the other. On 20 October 1918, Germany halted submarine warfare, and World War I concluded on 11 November 1918. The U-Boat Arm's final mission was to assist in the suppression of the Wilhelmshaven mutiny, which had erupted after the High Seas Fleet was ordered to Sea for a last, disastrous sortie. Following the Armistice, the remaining U-boats surrendered to the High Seas Fleet and were detained at Harwich. Over 8 million tons, or two-thirds of the 12.5 million tons of Allied shipping sunk in World Fighting I, were sunk in the Atlantic war zone. There were 153 Atlantic U-boats destroyed during the war, 77 from the far bigger High Seas Flotillas, and 76 from the much smaller Flanders force.