At the beginning of World War One the Germans had around twenty operational U-boats working with the High Seas Fleet. Initially they were deployed as a defensive screen; however, within days an ambitious plan was hatched to launch an attack on the British Grand Fleet at Scapa Flow. This was the operation in which U-15 was lost. U-5 and U-9 turned back because of engine problems, and U-18, although it managed to penetrate Scapa Flow, was sighted and sunk on 23 November 1914. Overall the German U-boats had lost 20% of their strength without claiming a single kill.
September 1914 had been a more promising month: U-21, commanded by Otto Hersing, had sunk the British light cruiser, HMS Pathfinder. He was to become a U-boat ace, launching twenty-one war patrols over a three-year period in which he sank thirty-six ships, including two battleships. As we have already seen, U-19 had claimed the three British destroyers off the Hook of Holland in September.
On 20 October 1914 an event took place that was to set the scene or terms of engagement for both world wars. Off southern Norway U-17 engaged the British steamer, SS Glitra. Kapitän-leutnant Feldkirchner boarded the vessel to inspect the cargo, after which he allowed the crew to board lifeboats, and then he sank the steamer.
On 26 October the pattern continued when Kapitän-leutnant Schneider on U-24 torpedoed SS Admiral Ganteaume without warning in the Dover Strait. This was the first time that a merchant vessel had ever been attacked in this way. Henceforth merchant vessels would become the prime target in attempts to wreck the economy of a wartime foe.
The significance of these two events was not lost on either the British or the Germans. The British had already mounted a blockade of Germany at a distance. Now the Germans felt confident enough to be able to launch their own counter blockade. Had they been able to maintain this blockade throughout the war perhaps the Allied victory would have been compromised.
By the end of 1914 the Germans had lost five U-boats, but had sunk ten merchant vessels and eight warships. On 18 February 1915, unrestricted U-boat warfare was introduced by the Germans. Henceforth any vessel found around the British Isles would be sunk without warning. Deciding whether a vessel was truly neutral was at the discretion of the U-boat captain.
The Germans lost Weddigen in March 1915 when U-29 was rammed by the British battleship HMS Dreadnought. His vessel was lost with all hands.
One of the most notorious submarine incidents took place on 7 May 1915. Kapitän-leutnant Schwieger, commanding U-29, fired a torpedo at RMS Lusitania to the south of Ireland. She sank in eighteen minutes and 1,200 people lost their lives, including 128 Americans. Controversy still rages around the loss of the vessel. She was registered as part of the British Fleet Reserve, she was in a war zone and arguably she was carrying munitions. However, such was the storm of protest from neutral America at the loss of her civilians that the German submarines were now ordered to ignore passenger liners.
On 19 August 1915, there was a similar but less well-known incident. Kapitän-leutnant Schneider (U-24), believing RMS Arabic to be a troop transport, sank her. But among the forty-four dead were three Americans. The Germans feared a backlash from the Americans, and as a consequence, on 20 September 1915, the U-boats were withdrawn from British waters, and for a while the primary area of operations became the Mediterranean.
By the end of 1915 the Germans had lost twenty U-boats, but had claimed 855,000 tons of shipping. The UC minelayers had claimed another ninety-four vessels. However, on 24 March 1916, UB-29, commanded by Oberleutnant Pustkuchen, sank the French cross-channel ferry, The Sussex, which had been mistaken for a minelayer. Eighty people were killed, among them twenty-five Americans. There was another enormous diplomatic row, and this time the Germans withdrew all of their vessels on 24 April.
For the Allies the losses were beginning to be serious, and new counter-measures were needed. Up to this point, with depth charges still under development, a submarine could only be destroyed by ramming it or hitting it while it was on the surface. The British now created the Q-ship.
As far as the U-boat was concerned, the Q-ship would look like a tramp steamer, but in reality it was armed with guns and torpedoes, and its cargo was wood or cork, in order to make it almost unsinkable. The Germans discovered to their cost that these Q-ships were incredibly dangerous. U-36 was sunk by HMS Prince Charles on 24 July 1915. Less than a month later U-29 was sunk by HMS Baralong. One of the hardest-fought engagements between a Q-ship and a U-boat took place on 8 August 1917, when an eight-hour battle took place between UC-71 and HMS Dunraven. In all, Q-ships managed to destroy fourteen U-boats and damage sixty others. Twenty-seven Q ships were lost.
In October 1916 U-boats returned to British waters, and in that month alone they sank 337,000 tons, and between November 1916 and January 1917 another 961,000 tons. In February 1917 a further 520,000 tons were sunk. U-boat successes steadily continued, reaching a peak in April 1917, when 860,000 tons were sunk.
With the USA finally declaring war on Germany in April 1917, the numbers of potential merchant victims soared. In the period May 1917 to November 1919, 1,134 convoys, consisting of 16,693 merchant vessels, made their way back and forth across the Atlantic. This new convoy system would lead directly to the defeat of Germany: she simply could not stop the flood of munitions, supplies and men. The tide had certainly begun to turn against the German U-boat threat.
According to the Armistice the 176 operational German submarines were handed over between November 1918 and April 1919. The German navy had started the war with twenty-eight U-boats; 344 had been commissioned and 226 were under construction when the war ended. The Germans had sunk over twelve million tons of shipping, or 5,000 ships. Seven submarine commanders, headed by Lothar von Arnauld de la Perière (450,000 tons) topped the list. The U-boats had been seen to be a powerful, though not a decisive, weapon of war. The 176 operational U-boats handed over to the British were evaluated, stripped, parcelled out to Allies or scrapped. Germany was then prohibited from building or possessing U-boats.