WWI [blue] and WWII [green] U-boats Compared.
When World War I commenced in early August 1914, the German Imperial Navy had not completed its big-ship buildup. The High Seas Fleet was therefore not strong enough to sail out and confront Britain’s powerful Grand Fleet in a single, decisive battle. Nor was the Royal Navy capable of mounting a decisive attack on the Imperial Navy in its home waters. Hence a big-ship standoff ensued, during which the opposing admirals schemed ways to entrap the other’s fleet in the confined waters of the North Sea by guile and deception. The naval war between these two great maritime powers thus proceeded in a curious, cautious, and unforeseen manner. There was only a single major surface-ship battle—Jutland—and it was brief and inconclusive.
Early in the war both Germany and Great Britain deployed submarines on offensive missions. The initial forays were remarkable. German U-boats sank three British heavy cruisers (Aboukir, Hague, and Cressy) and two light cruisers (Pathfinder, Hawke) with the loss of over 2,000 men. British submarines sank the German light cruiser Hela. Both navies were thus compelled to view the submarine as a grave new threat and they reacted accordingly. The British Grand Fleet withdrew temporarily from its North Sea base in Scapa Flow to safer waters in north Ireland. The German High Seas Fleet sharply curtailed operations in its home waters, the Helgoland Bight.
The British imposed a naval blockade against Germany with the aim of shutting off the flow of war matériel. The British did not strictly observe the prize laws; even neutral ships loaded merely with food were harassed, blocked, or turned back. In retaliation, the German Naval Staff authorized German U-boats to harass Allied merchant shipping. On October 20, 1914, a U-boat, observing the prize laws, stopped, searched, and scuttled the 866-ton British freighter Glitra off Norway. A week later another U-boat, operating in the English Channel, torpedoed without warning a French steamer, Admiral Ganteaume, which was believed to be laden with troops and therefore fair game under the prize laws. In fact the ship was jammed with 2,400 Belgian refugees, including many women and children. Fortunately, it did not sink.
These two U-boat attacks on unarmed merchant ships carried profound implications for the island nation of Great Britain, entirely dependent upon her vast mercantile fleet for survival. An organized U-boat guerre de course might be ruinous. Accordingly, the British government denounced the attacks as illegal, treacherous, piratical, and immoral. Ship owners, merchants, and insurance carriers the world over joined the chorus of denunciation.
The Central Powers, composed of Germany and the Austro-Hungarian Empire, had planned to defeat France in a quick campaign, then turn about and crush czarist Russia. But the plan went awry. The armies in France bogged down in bloody trench warfare; Russia attacked from the east, creating a two-front war. Not having anticipated a long war, the Central Powers had not stockpiled large supplies of war matériel. As a result of the British blockade, by early 1915 the Central Powers were running out of iron ore and oil and other war essentials as well as food.
To this point U-boats, strictly observing the prize rules, had sunk ten British merchant ships for about 20,000 tons. Owing to the shortage of torpedoes—they were still virtually handmade—most of these sinkings had been achieved by gunfire or forced scuttling. The surprising ease of these successes had led the senior German admirals to conclude that if the prize rules were relaxed, even the small number of U-boats available for distant operations could impose an effective counterblockade on the British Isles. The mere appearance of a single U-boat, manned by only two dozen men, whether successful in the attack or not, caused great psychological alarm, compelling the enemy to devote a hugely disproportionate share of his manpower and resources to neutralize the threat. All this would severely impair Britain’s ability to carry on the war, the advocates postulated, and might result in a tit-for-tat deal in which Britain agreed to lift its blockade of Germany.
Neither the Kaiser nor his Chancellor was keen on the proposal. Germany had already incurred heavy criticism from many quarters for sinking merely ten merchant ships. A relaxation of the prize rules would doubtless draw even harsher criticism, especially from neutral nations such as the United States, which had a substantial financial interest in sea commerce and might retaliate by entering the war. Moreover, the number of U-boats available for blockading the British Isles seemed too slight. To announce a blockade and fail abjectly would be worse than no attempt at all.
And yet the proposal would not die. Its advocates argued, not without justification, that the moral arguments were no longer relevant. In its ruthless blockade of Germany, they insisted, Britain had repeatedly violated the prize rules and other traditions protecting sea commerce, most notably in refusing the passage of neutral ships carrying only food. This line of reasoning, and other arguments, finally persuaded the Kaiser and his Chancellor to authorize a U-boat blockade of Great Britain.
The stage was carefully set. The Kaiser publicly declared that from February 18, 1915, onward, the waters around the British Isles were to be considered a “war zone.” Prize rules would no longer be strictly observed. British and French merchant vessels would be sunk without warning or exceptional measures to provide for the safety of the crews. Care would be taken to spare neutrals not carrying contraband, but all neutrals would sail the waters at their own peril. U-boat skippers, the Kaiser further declared, would not be held responsible if “mistakes should be made.”
So was launched history’s first systematized submarine guerre de course. The initial results were less than impressive. In the month of February 1915, the twenty-nine U-boats of the German submarine force sank 60,000 tons of merchant shipping; in March, 80,000 tons. The weakness of the blockade lay in the small number of U-boats available. Owing to the time spent going to and from German bases and in refit, after the initial deployment it was difficult to establish organized U-boat patrol cycles that kept more than six or seven U-boats in British waters at any given time. Notwithstanding the fear and confusion and diversion of resources it precipitated, the first U-boat blockade did not achieve its main goal. First Lord Churchill declared the blockade a failure; British imports in 1915 exceeded those of 1913. The British government refused to entertain any suggestion of lifting the blockade of Germany.
With each merchant ship sinking, the cries of moral indignation intensified. Three sinkings in particular outraged the Americans: the 32,500-ton Cunard liner Lusitania on May 7, with the loss of 1,198 passengers (128 Americans) and crew; the 16,000-ton White Star liner Arabic on August 19, with the loss of 40 passengers (3 Americans); and the liner Hesperian on September 9. So violent was the reaction in the United States (U-boat crews make war “like savages drunk with blood” declared The New York Times), that in early September 1915 the Kaiser called off the blockade of Great Britain and sent many more U-boats to the Mediterranean Sea, where the hunting was less controversial and no less lucrative and there were few Americans.
With victory no closer for the Central Powers, at the beginning of 1916 the chief of the German naval staff, Admiral Henning von Holzendorff, and his Army counterpart urged the Kaiser to authorize a renewal of the British blockade. The Navy now had almost twice as many U-boats in commission (fifty-four versus twenty-nine in 1915) and ever more U-boats were coming off the slipways. The Kaiser was tempted, but the Chancellor and Foreign Minister objected, fearful of another Lusitania, which would almost certainly bring America into the war. After days of vacillation, the Kaiser sided with the Navy, but he imposed complicated restrictions. No passenger liners of any nationality were to be attacked anywhere. No cargo ships or tankers except those unmistakably armed could be attacked outside the war zone.
The renewed blockade commenced in February 1916. Notwithstanding the restrictions and complexity of the rules, all went well for the U-boats for two months: 117,000 tons sunk in February, 167,000 tons in March. Then came another costly error. On March 24 a U-boat mistook the 1,350-ton English Channel passenger ferry Sussex for a troopship and torpedoed it. The Sussex did not sink, but about eighty people were killed in the explosion, including twenty-five Americans. In response to the renewed cries of indignation and a blistering note from Washington threatening to sever diplomatic relations, the Kaiser backed down once more and, on April 24, ordered U-boats in waters of the British Isles again to adhere strictly to the prize rules. As a result, merchant ship tonnage sunk by U-boats in British waters fell sharply for the next four months.
The German submarine force had grown to substantial size by September 1916: a total of 120 boats of all types, many with larger 105mm (4.1”) deck guns. Again the military staffs urged the Kaiser to exploit this force to the fullest. Again the Kaiser vacillated, and finally yielded, but with yet a new set of rules. Skippers were to conduct only restricted submarine warfare (by prize rules) in waters of the British Isles, where there were numerous American and other neutral ships, but they were permitted to wage unrestricted submarine warfare in the Mediterranean. This third and most intense phase of the restricted U-boat war, October 6, 1916, to February 1, 1917, was highly productive for the Germans. The U-boats sank about 500 British merchant vessels for about 1.1 million tons, raising the total bag for 1916 to about 2.3 million tons, most of that of British registry.
By early 1917 the ground war had become a brutal and fruitless bloodletting for the Central Powers and there was deep and widespread unrest at home. The German military staffs urged the Kaiser to authorize unrestricted submarine warfare in all oceans and seas. Using the results achieved in the fall of 1916, the larger number of U-boats available, plus nearly ninety new boats that were to be commissioned in 1917, the naval staff calculated that with an unrestricted U-boat campaign, nearly half of Britain’s still large merchant fleet could be wiped out within five or six months, rendering her not only incapable of prosecuting the war on the continent but also leaving her population in a condition of starvation and rebellion. America be damned, the naval staff said. If she came into the war, Germany would have enough U-boats (about seventy ready for operations in the British Isles alone) to sink all her troop and supply ships before they reached Europe. By that time, too, there was no shortage of German submarine torpedoes; U-boat skippers did not have to rely so heavily on deck guns.
Turning aside peace feelers from President Wilson and others, the Kaiser approved this proposal. He announced to the world that commencing February 1, 1917, U-boats would sink on sight every merchant ship found in British territorial waters. At the same time, he assured the German military staffs that there would be no more pussyfooting or backing down, and he promulgated a radical role reversal for the surface ships of the Imperial Navy: Henceforth they were to support U-boats, rather than the other way around. “To us,” he said, “every U-boat is of such importance that it is worth using the whole available fleet to afford it assistance and support.”
Germany launched this all-out submarine guerre de course in the British Isles with multiple attacks conducted simultaneously with “utmost energy” by about sixty U-boats. To minimize detection by Allied aircraft and submarines, and counterfire from merchant ships, and to take advantage of higher speed for escape, U-boat skippers attacked at night while on the surface. The results were spectacular: 540,000 tons sunk in February, 594,000 tons in March, and an appalling 881,000 tons in April. During April alone—the grimmest month of the U-boat war—the Germans sank 423 merchant ships, of which 350 were British.* Moreover, as anticipated, the campaign scared off most of the many neutral ships trading with Great Britain.
Reflecting the growing anger and outrage in America, President Wilson reacted firmly and militantly to this all-out U-boat campaign. On the third day, February 3, 1917, he broke off diplomatic relations with Germany. At his request, on April 6 the Congress declared war on the Central Powers.
At the beginning of the war the Royal Navy possessed no special countermeasures to fight submarines. Naval tacticians wrongly assumed that since submarines would of necessity spend most of the time on the surface, they would be easy prey for gunfire and ramming. This wrong view was reinforced when the British cruiser Birmingham rammed and sank U-15, the first U-boat to be lost. But in the five months of warfare in 1914, the Royal Navy positively sank only one other U-boat, U-18. Three other U-boats were lost in 1914 (for a total of five) to unknown causes, probably mines.