Holtzendorff decided that the U-boat campaign had not achieved its goal, and on 18 September ordered that for the next few weeks there would be no submarine attacks on merchant shipping off the west coast of Great Britain or in the English Channel; in the North Sea submarine warfare would be conducted strictly according to prize law.48 The effect of this was to end the first submarine campaign against commerce. Submarines shifted back to primarily military tasks while the Germans began to build up their strength in the Mediterranean, where they found favorable opportunities and fewer risks of incidents with the United States (see chapter 12). It is important to remember, however, that by the admission of the Germans themselves, the suspension of activity by the North Sea flotillas “did not work quite so much hardship,” because after the detachment of the U-boats to the Mediterranean, only four of the remaining U-boats available for operations on the west coast of Great Britain did not need extensive repairs.49
The bitterness among the naval leaders remained, and Tirpitz continued his opposition, constantly seeking outside support until his resignation in March 1916. He went back to what Müller termed his “old refrain” on 3 December, arguing that “the Fleet must be engaged or otherwise the Kaiser’s life work would be destroyed,” and that he would be ready to take over the fleet himself.50 One can guess the atmosphere by the derogatory names applied to naval leaders. Müller was known as “Rasputin,” Holtzendorff as “the father of the lie,” and Capelle (Tirpitz’s successor at the Reichsmarineamt) as “Judas Iscariot.”51
It is interesting to examine what effect the first submarine campaign had on the British and their allies. The first three months, February, March, and April, were not very effective and British and Allied communications were not interrupted. The rate of sinking was actually lower than it had been at the height of the cruiser campaign at the beginning of the war, and thanks to new construction and the capture of enemy shipping, the tonnage available to the British actually rose. The British were able by diplomatic measures to tighten the blockade and exploit neutral shipping. Neutrals were definitely not frightened away. There was, however, an increasing shortage of tonnage for commercial purposes due to requisitioning of ships for naval and military purposes, redistribution of trade, and congestion of ports. The period was perhaps deceptive for the British, as losses were low not because of the effectiveness of antisubmarine operations but because the number of submarines actually operating was still small.52
Losses from June to September 1915 rose considerably to the point where they surpassed the old rate of sinking under cruiser warfare and the rate of new construction. The losses, however, were still small in proportion to the total volume of traffic. On 31 July, the end of the first year of war, the total British losses from all causes in steamers of 1,600 tons or larger was under 4 percent in numbers and a little more than 3.5 percent in tonnage. August was a shock, for the average monthly loss in numbers or tonnage, which had been under one-third of 1 percent, rose to .92 percent in numbers and .78 percent in tonnage. Losses fell in September to .53 percent in numbers and .47 percent in tonnage, still above the previous average. The monetary value of losses in ships and cargo was so high that but for the spreading of risks through the State Insurance Scheme, the losses would have been so onerous to individual owners and merchants that trade might have been paralyzed. In terms of losses and gains, from August 1914 to September 1915, total losses in tonnage were 1,294,000 tons, whereas 1,233,000 tons were added through new construction and 682,000 tons were added through the capture or detention of enemy ships. However, the total tonnage available was now a diminishing figure, for new merchant tonnage steadily declined. This was probably due to the diversion of men and matériel to purely naval construction as well as the enlistment of many workers. The demands on tonnage for overseas expeditions—the Dardanelles, Mesopotamia, and Salonika—also increased. The heavy losses of August 1915 were also an indicator of the potential of the submarine, and Admiral Hezlet concludes that it was undoubtedly a great relief when the Germans called off the first submarine campaign.53
THE “RESTRICTED” SUBMARINE CAMPAIGN
The German navy now entered into what is sometimes called the “twilight phase” of submarine warfare, which lasted, except for two months (March-April 1916), until September of 1916. It was also a period in which the High Sea Fleet returned to active surface operations, resulting in the Battle of Jutland and the near-battle of 19 August. Restricted submarine warfare is also a very loose term, for the Germans tended to go as far as they thought they could get away with, and the term had less meaning for the Mediterranean. The Flanders Flotilla, which was frustrated at having its activities curtailed just as the long nights of autumn and winter were approaching, resorted increasingly to mine warfare with the new UC boats. On 21 November 1915, Holtzendorff ordered the Flanders Flotilla to sink enemy freighters without warning in the zone between Dunkirk and Le Havre, although the measure was not really practical until the new UB.II boats were available in mid-February 1916. On 24 January 1916, the kaiser agreed to the sinking without warning of armed enemy freighters, and on 13 March to sinking without warning all enemy freighters within the war zone. The rules were therefore constantly changing according to the diplomatic situation.54
A German submarine commander complained after the war of the numerous restrictive orders:
As a matter of fact, so many were issued that it was impossible for a submarine commander to learn them all, and many a time it was necessary for the helmsman or some other trusty support to bring the orders to the conning tower and hastily run through the mass to find out whether or not a certain vessel could be torpedoed. Even then it frequently turned out that “whatever you do is wrong.” For a commanding officer to be continually harassed by the thought that he will be held accountable for this or that sinking, when returning from a long and arduous cruise, makes his task especially difficult.55
Although originally brought into office to restrain the U-boat zealots, Holtzendorff was converted to the idea of unrestricted submarine warfare by the end of 1915. He apparently was convinced by the report of a group of German shipping experts, which, correctly, took account of the substantial portion of British merchant tonnage now devoted to military purposes combined with the reduction in new tonnage from the shipbuilding yards because of the diversion of men and matériel. They calculated the amount of new tonnage likely to enter service in 1916, then an average monthly loss of so many thousand tons achieved by a force of thirty-five U-boats. They theorized that a force of U-boats doubled in size would inflict twice the losses, and subtracting these forces from new construction, the British would be forced to end the war within six to eight months. The United States could be safely disregarded. Even if the Americans entered the war, they would not be likely to be able to render any significant assistance within this time. Holtzendorff in January 1916 confidently predicted that, based on past performance, they could assume in the future each U-boat would sink at least 4,000 tons daily and that, counting U-boats on station in the North Sea and Mediterranean and adding average losses from mines, they could sink 631,640 tons per month for a six-month total of almost 3.8 million tons. The full argument was, of course, more sophisticated than this crude summary. It also reflected how the submarine had changed the nature of the war at sea for naval staffs. It was now a question of graphs and curves; “tonnage” was the important word rather than individual ships or men.
Holtzendorff won the support of Falkenhayn, who planned to weaken England’s foil on the Continent, the French army, through a massive battle of attrition—the battle of Verdun, which began on 21 February—but did not believe he could achieve a final decision against the British on land. The submarine campaign consequently was a powerful auxiliary in discouraging the British from continuing the war. Tirpitz, ever fractious, did not believe any single weapon, even submarines, could defeat England, but believed submarines could so increase Great Britain’s difficulties that the British would give way.
There were other factors as well. The commander of the High Sea Fleet, von Pohl, was a sick man and died of cancer in February 1916. He was replaced on 8 January by Vice Admiral Scheer, much more vigorous, far more offensively minded, and an ardent partisan of U-boat warfare. The spread of the practice of arming merchantmen also gave German advocates of unrestricted submarine warfare another lever. Their small submarine force in the Mediterranean had done extremely well, but in mid-January 1916 the Mediterranean U-boat flotilla commander Korvettenkapitän Kophamel warned that too many armed steamers were escaping from submarines. He argued that a steamer armed by its government was really a warship—some even had military gun crews on board—and there were no armed “merchant ships” unless they were pirates. He recommended notifying neutrals that all armed steamers would be treated as warships and sunk on sight. The Germans also were encouraged by the well-meaning proposal of the American secretary of state, Robert Lansing. This so-called modus vivendi proposal sought to recognize the changed conditions of war. German submarines ought to obey international law by stopping and searching vessels and assuring the safety of passengers and crew before they were sunk. In turn, the British and French would have to stop arming merchant vessels, which, if they were armed, would be treated as auxiliary cruisers. This argument, needless to say, was rejected by the British, but the combination of circumstances was sufficient to overcome the objections of Bethmann Hollweg and lead the German government to resume “sharpened,” if not totally unrestricted, submarine war.56
The Germans followed a somewhat confusing course on the question of unrestricted submarine warfare that must have exasperated submarine commanders. On 3 February Holtzendorff informed Kophamel that as of 20 February armed British and French steamers in the Mediterranean could be attacked without warning. On 11 February the order bearing the kaiser’s signature was issued to the fleet that as of 29 February armed enemy merchant vessels could be sunk without warning, but that submarine commanders should bear in mind that mistakes would lead to rupture of diplomatic relations with neutrals and that they should destroy a merchant ship because of its armament only if its armament was clearly recognized. Neutral vessels remained exempt. Holtzendorff issued a supplement to these orders, directing submarines that had attacked while submerged not to surface after firing the torpedo, but to depart while still under water. Submarine commanders could also treat merchant ships as warships when they had been listed by the Admiralstab as armed, even if their armament was not clearly discernible, as long as there was no doubt about their identity.
The kaiser, influenced by Bethmann Hollweg, hesitated at the implications of unrestricted submarine warfare. When he met the new commander in chief of the High Sea Fleet aboard the latter’s flagship Friedrich der Grosse on 23 February, he counselled sparing passenger liners and remarked, “Were I the Captain of a U-boat I would never torpedo a ship if I knew that women and children were aboard.” The Admiralstab therefore issued the order that passenger liners were not to be attacked, even if they were armed. The United States, however, continued to protest the proposed treatment of armed merchant vessels as warships, and the crisis within the German government continued. A crown council met at Charleville on 4 March, but a clear decision regarding unrestricted submarine warfare was not forthcoming. The kaiser concluded unrestricted submarine warfare against Great Britain was unavoidable and would probably begin on 1 April, but until then Bethmann Hollweg was ordered to try and secure American understanding for the German position with the objective of giving Germany a free hand. Until an agreement with the Americans was reached, German submarines would operate under the orders of 1 March, which provided for what might be termed “sharpened,” as opposed to “unrestricted,” submarine warfare. Enemy merchant ships inside the war zone would be destroyed without warning; enemy merchant ships outside the war zone would be destroyed without warning if they were armed. Passenger liners, either inside or outside the war zone, could not be attacked from under water whether they were armed or not. The orders permitting attacks on troop transport between Le Havre and Dunkirk remained in effect. Tirpitz, who was not invited to the meeting, resigned. This time his resignation was accepted, and he was replaced by Vice Admiral Eduard von Capelle.57
What was the German U-boat strength as they prepared to embark on a second submarine campaign? In March 1916 there were 52 operational boats, compared to 29 to 30 at the start of the first campaign. There were 16 U-boats in the North Sea, 20 in the Flanders Flotilla (8 UB.I, 4 UB.II, and 8 UC.I), 4 in the Baltic, 7 in the Adriatic, and 5 at Constantinople. The Germans could reasonably expect 38 of the U-boats under construction to enter service in the period between April and August of 1916. As for the future, at the beginning of the year Tirpitz had inquired how many UC.II minelayers could be finished by the end of the year if all new shipbuilding and torpedo-boat projects that would not be completed until after the start of the new year were deferred. The U-Boat Inspectorate determined the total to be 31, and the boats were promptly ordered on 11 January 1916. This was the largest single order of the war to date, representing the enhanced importance given to minelaying, given the other restrictions on submarine warfare. The smaller UC boats took priority because they could be finished fairly quickly. Nevertheless, in late May the Imperial Naval Office also ordered 12 large, long-range (10,000 miles at 8 knots) “Project 42” submarines (U.127 to U.138), armed with six torpedo tubes and two 10.5-cm guns to act as offensive U-boat cruisers against merchant shipping. At virtually the same time they also ordered 10 large long-range minelayers (U.117 to U.126), capable of carrying 42 mines plus an additional 30 in deck containers. The delivery times on these large and complex boats were necessarily long, and the Imperial Naval Office therefore ordered in early May 24 UB.III-class medium-sized boats suitable for operations around the British Isles and in the Mediterranean. The boats were more powerful than those of the UB.II class, with larger caliber torpedoes and an 8.8-cm gun. The last of the boats was supposed to enter service by April 1917, but once again the yards made overly optimistic delivery promises and the last of the boats was seven months late.58
The sharpened U-boat offensive was once again curtailed by diplomatic rather than military factors. The neutral Dutch were hard hit. On 16 March the Royal Holland Lloyd liner Tubantia (13,911 tons), outward bound for Buenos Aires, was torpedoed and sunk near the North Hinder light vessel by UB.13. The Tubantia was the largest neutral ship sunk by submarines during the war. Two days later the Germans sank another Dutch steamer, the Royal Rotterdam Lloyd liner Palembang (6,674 tons). The Dutch packets that plied the North Sea between the Netherlands and Great Britain were decimated by German actions. On 1 February the Princess Juliana (2,885 tons) was beached near Felixstowe after hitting a mine laid by UC.5 and became a total loss. Her sister ship the Mecklenburg (2,885 tons) was sunk on 27 February by a mine laid by UC.7. On 16 May the Rotterdam-London packet Batavier V (1,568 tons) was mined and sunk near the Inner Gabbard light vessel. Other Dutch packets were captured by the Germans and taken into Zeebrugge. Some were released, but others, such as the Zaanstroom (1,657 tons), captured by a German submarine in March 1915, were retained. The harassment, losses, and damage continued throughout the war. It is hardly surprising that the Dutch press was furious and the Dutch parliament spoke of military preparations. The Dutch subsequently laid up a few of their largest and most valuable liners for the duration of the war. It was not easy to be a small neutral next door to great powers at war.
The Netherlands was a small neutral whose military potential was limited. The United States was a large neutral with great potential; consequently the most serious incidents from the German point of view involved Americans. On 24 March Oberleutnant zur See Pustkuchen in UB.29 torpedoed without warning the French cross-Channel steamer Sussex (1,353 tons) off Dieppe. The steamer managed to reach port, but there were fifty fatalities, including some of the twenty-five U.S. citizens on board. The submarine had not been seen, and the German suggestion t
hat the Sussex might have been damaged by a mine was disproved after fragments of a torpedo were found in one of the lifeboats. In his limited view through the periscope, Pustkuchen had assumed the passengers crowding the Sussex’s deck were troops. The Sussex was actually in an area where submarines had been authorized to attack without warning since the preceding November, but it was only after UB.II-class boats, such as UB.29, came into service that they had been able to exploit the order. The young officer had plunged his government into a major diplomatic crisis, for the Sussex incident seemed a direct challenge to President Wilson, and on 20 April the United States delivered what amounted to an ultimatum, threatening to sever diplomatic relations if the Germans did not abandon their present methods against passenger and freight carrying vessels.
A Naval History of World War I Page 53