The Atlantic U-boat campaign of World War I (sometimes called the "First Battle of the Atlantic", in reference to the World War II campaign of that name) was the prolonged naval conflict between German submarines and the Allied navies in Atlantic waters –the North Sea, the seas around the British Isles, and the coast of France.
Initially the U-boat campaign was directed against the warships of the British Grand Fleet, which were, along with other Entente powers, enforcing the Naval Blockade of Germany. When the blockade extended to merchant ships and foodstuffs, U-boat fleet action was likewise extended to include action against the trade routes of the Allied powers. To counter the German submarines, the Allies moved shipping into convoys guarded by destroyers, blockades such as the Dover Barrage and minefields such as the North Sea Mine Barrage were laid, naval vessels disguised as merchant ships were constructed, indicator loops were strung across lengths of the North Sea, and aircraft patrols monitored the U-boat bases. Increased ship construction meant the amount of Allied shipping available remained fairly stable.
The U-boat campaign was not able to cut off supplies before the US entered the war in 1917, and in late 1918 the U-boat bases were abandoned in the face of the Allied advance.
1914: Initial campaign
First patrols
On 6 August 1914, two days after Britain had declared war on Germany, 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 to attack Royal Navy warships in the North Sea.
The U-boats sailed north, hoping to encounter Royal Navy squadrons between Shetland and Bergen. On 8 August, one of U-9's engines broke down and she was forced to return to base. On the same day, off Fair Isle, U-15 sighted the British battleships HMS Ajax, Monarch, and Orion on manoeuvres and fired a torpedo at Monarch. 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. There was no sign of any lookouts on the U-boat and it was reported that sounds of hammering could be heard, as though her crew were performing repairs. 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 and her crew was also missing, and were thought to have been mined or otherwise lost in an accident. 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 action
On 5 September 1914, U-21 commanded by Lieutenant Otto Hersing made history when he torpedoed the Royal Navy light cruiser HMS Pathfinder. The cruiser's magazine exploded, and the ship sank in four minutes, taking 259 of her crew with her.
The German U-boats were to experience further success on 22 September. Early in the morning of that day, a lookout on the bridge of U-9, commanded by Lieutenant Otto Weddigen, spotted a vessel on the horizon. Weddigen ordered the U-boat to submerge immediately, and the submarine went forward to investigate. At closer range, Weddigen discovered three old Royal Navy armoured cruisers, HMS Aboukir, Cressy, and Hogue. These three vessels were staffed mostly by reservists, and were so clearly vulnerable that a decision to withdraw them was already filtering up through the bureaucracy of the Admiralty. The order did not come soon enough for the ships. Weddigen 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, Weddigen also sank the old cruiser HMS Hawke, and the crew of U-9 became national heroes. Each was awarded the Iron Cross Second Class, except for Weddigen, who received the Iron Cross First Class. 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.
On 18 October, SM U-27 sank HMS E3, the first instance of one submarine sinking another.
End of the first campaign
These concerns were well-founded. On 23 November U-18 penetrated Scapa Flow via Hoxa Sound, following a steamer through the boom and entering the anchorage with little difficulty. However, the fleet was absent, being dispersed in anchorages on the west coast of Scotland and Ireland. As U-18 was making her way back out to the open sea, her periscope was spotted by a guard boat. The trawler Dorothy Gray altered course and rammed the periscope, rendering it unserviceable. U-18 then suffered a failure of her diving plane motor and the boat became unable to maintain her depth, at one point even impacting the seabed. Eventually, her captain was forced to surface and scuttle his command, and all but one crew-member were picked up by British boats.
The last success of the year came on 31 December. U-24 sighted the British battleship HMS Formidable on manoeuvres in the English Channel and torpedoed her. Formidable sank with the loss of 547 of her crew. The C-in-C Channel Fleet, Adm. Sir Lewis Bayly, was criticized for not taking proper precautions during the exercises, but was cleared of the charge of negligence. Bayly later served with distinction as commander of the anti-submarine warfare forces at Queenstown.
1915: War on commerce
First attacks on merchant ships
The first attacks on merchant ships had started in October 1914. On 20 October 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, under the command of Kapitänleutnant Johannes Feldkirchener. 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 people died, mainly due to panic. The U-boat's commander, Rudolf Schneider, claimed he had mistaken her for a troop transport.
On 30 January 1915, U-20, commanded by Kapitänleutnant Otto Dröscher, torpedoed and sank the steamships Ikaria, Tokomaru and 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.
In February 1915, Admiral Hugo von Pohl, commander of the German High Seas Fleet and Head of the Admiralty Staff until 1 Feb, escalated the conflict by declaring the waters around Britain and Ireland to be a "war zone". Though attacks by U boats on merchant ships had transpired previously despite the stated rules of engagement, his declaration included merchant ships and neutral vessels among the new list of officially valid targets. In March 1915, a Maritime Order in Council declared that the British would seize any ships headed to, coming from, or with ownership in Germany, extending previous permissions to seize ships carrying contraband.
The decision to target merchant ships was not taken lightly according to U-Boat Captain Franz Becker, who stated:
The war with the submarines was a serious matter. At the beginning of the war, it was not easy for us to sink merchant ships, because we would have preferred to make the war against warships. Because every merchant ship we had some personal contact with them. I remember, especially, one day I met a very fine one of the last big sailing ships and to sink it, it was very, very heavy for me. But then we went home on leave to Germany and we could see how Germany was blockaded; our people in Germany had hunger. And then we had new forces to make the war with submarines against merchant ships. We needed to know this; why we did this war against merchant ships.
Unrestricted submarine warfare
One British concern regarding unrestricted submarine warfare was its effects on the import of foodstuffs; W. T. Stead wrote in 1901 that without these imports "We should be face to face with famine". Arthur Conan Doyle wrote a short story, Danger! that illustrates the defeat of the UK using only a small number of submarines. Inspired in part by such tales, German Admirals like von Tirpitz and Hugo von Pohl agitated for a campaign against British commerce with no restrictions, despite the tiny number of submarines available (21 at the start of 1915, 7 of which were undergoing repair work). On 4 February 1915, the first unrestricted campaign against Allied trade was formally started.
In the first month 29 ships totalling 89,517 GRT 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, U-8 torpedoed Belridge, a neutral tanker travelling between two neutral ports; in March U-boats sank Hanna and Medea, a Swedish and a Dutch freighter; in April two Greek vessels.
In March also, Falaba was sunk, with the loss of one US life, and in April Harpalyce, a Belgian Relief ship, was sunk. On 7 May, U-20 sank RMS Lusitania with the loss of 1,197 lives, 124 of them US 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. This response freed the U-boat to attack without warning, however. On 20 March 1915, this tactic was used by the Great Eastern Railway packet Brussels to escape an attack by U-33. For this her captain, Charles Fryatt, was executed after being captured by the Germans in June 1916, provoking international condemnation.
While another option was arming ships for self defence, this, according to the Germans, put them outside the protection of the cruiser rules, potentially endangering the ships further.
Another option was to arm and man decoy ships with hidden guns, known as Q-ships. 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, U-40 was sunk by HMS C24 while attacking Taranaki, and in July U-23 was sunk by C-27 attacking Princess Louise. Also in July U-36 was sunk by the Q-ship Prince Charles, and in August and September U-27 and U-41 were sunk by Baralong, the former in the notorious Baralong Incident.
British Sailor Henry Claxton described Q-ships as such:
A Q boat was a merchant ship or a sea-going trawler that was disguised. Seeing it through binoculars it looked just an ordinary merchant ship or an ordinary sailing ship. But behind all the façade were guns hidden up out of sight. Well, when a U-boat spotted this, they were wary of what it was and that. And directly the U-boat made itself known, a panic party used to leave this ship, as though they were deserting the ship. But left onboard was the remainder of the crew hidden away there, out of sight, and there's the ship – to all intents and purposes – deserted. And the U-boat would gradually come nearer and when she was within range, say 100 or 200 yards, and directly the skipper on board thought the time was right, down flaps. And before the U-boat could get away she's had her chips.