The Holtzendorff memorandum of 22 December 1916 is well known, for most of it was published by Scheer in his memoirs immediately after the war.8 A rough summary of Holtzendorff’s argument is as follows. A decision in the war would have to be reached by the autumn of 1917 lest it end in the exhaustion of all parties and, consequently, disastrously for Germany. Italy and France were really sustained only by Great Britain’s energy and activity, and if they could break Britain’s back the war would at once be decided in Germany’s favor. Britain’s backbone (Rückgrat) was tonnage (Schiffsraum), which at the moment amounted to 20 million gross tons. At least 8.6 million tons of this were requisitioned for military purposes, half a million tons were occupied in coast traffic, about a million tons were under repair or temporarily unfit for use, and about 2 million tons were necessary to supply the needs of Great Britain’s allies. This left at most 8 million tons available for Great Britain’s own supplies. The statistics concerning traffic in British ports gave even smaller results. From July to September 1916, only 6.75 million gross tons of British shipping was engaged in traffic to Great Britain. There was also an estimated 900,000 gross tons of seized German and Austrian shipping and about 3 million gross tons of neutral shipping proceeding to England. This gave a rough total of only 10.75 million gross tons of shipping supplying the British.
The poor harvest in wheat and produce throughout the world gave the Germans another opportunity. North America and Canada would probably be unable to send additional grain to Great Britain after February, and the British would be forced to import grain from distant Argentina. However, the Argentines had also experienced a bad harvest and could spare little, which in turn would force the British to import from India and, above all, from Australia. The greater distances involved would force the British to use an additional 720,000 tons for grain shipments. This meant that until August 1917 the British would have to use three-quarters of a million tons of the 10.75 million tons at their disposal for purposes that had not previously been necessary. Holtzendorff repeated earlier statements that it was absolutely unjustifiable not to make use of the U-boat and made the flat assertion that as matters now stood, the Germans could force England to make peace in five months through unrestricted submarine warfare. He emphasized, however, it would have to be real unrestricted warfare, and not merely cruiser warfare in which the submarines were only allowed to attack all armed steamers.
Holtzendorff calculated that based on the former results of 600,000 tons of shipping per month sunk by unrestricted submarine warfare and the expectation that at least two-fifths of the neutral traffic would instantly be terrorized into ceasing voyages to Britain, the Germans after five months could count on reducing traffic to and from Britain by about 39 percent. The British could not bear this, for reasons Holtzendorff described (which are too lengthy to reproduce here). Cruiser warfare waged by U-boats would only result in about half the estimated sinkings of unrestricted warfare and would therefore not have the desired results.
Holtzendorff minimized the potential consequences of war with the United States. Certainly it would be a serious matter and everything ought to be done to avoid it, but “fear of a break must not hinder us from using this weapon which promises success.” The effect on tonnage “can only be very small,” and it was not probable more than a small fraction of the tonnage belonging to the Central Powers lying in American and neutral ports would be quickly available for voyages to England. The Germans had made preparations to sabotage the greater part of it to such an extent that it would be useless during the first months, which would be the decisive period. Moreover, the crews would not be available to man them, nor could American troops be brought over in considerable numbers owing to the shortage of shipping. Holtzendorff added that American money could not make up for the shortage of supplies and tonnage. He emphasized that the unrestricted submarine campaign must begin no later than 1 February, so as to ensure peace before the next harvest, that is, 1 August.
Holtzendorff’s argument contained, as we shall see, a number of false assumptions, but the constellation of forces favoring unrestricted submarine warfare was able to overwhelm the objections or hesitations of their opponents, and at the Schloss Pless conference of 9 January 1917, the Germans reached the fateful decision to commence unrestricted submarine warfare on 1 February. Bethmann Hollweg felt he could no longer oppose, given the opinion of the general staff and naval leaders. For the chancellor, it was not so much approval as an acceptance of the facts.9
The Germans had 105 U-boats available on 1 February. They were deployed as follows: High Sea Fleet, 46; Flanders, 23; Mediterranean, 23; Kurland (Baltic), 10; and Constantinople, 3. Thanks to new construction, and despite losses, U-boat strength rose steadily to a peak of 129 on 1 June; for the remainder of the year it did not fall below 120, ending the year at 125.10 The U-boat construction program itself remained plagued by difficulties, exacerbated by the severe winter of 1916–17, which brought shortages of coal, difficulties in transport, and poor morale among workers. The situation was serious enough for Hindenburg to send a special emissary to the U-Boat Inspectorate at Kiel on 15 January to examine the problems. The high command agreed to give priority to the transport of certain raw materials and components necessary for submarine construction and furnish the names of soldiers skilled in U-boat construction who might then be released from the army. Capelle and the Reichsmarineamt were anxious to get as many boats into action within the shortest possible time and therefore did not intend to order boats that could not be delivered by the beginning of 1918. This in practice meant most orders were for the medium-sized UB.III class, which had a relatively short building time and were handy and well suited for operations around the British Isles or in the Mediterranean.
In February contracts were signed for 45 UB.III boats (UB.88 to UB.132) as well as for 6 of the larger Ms boats. The orders, given attrition, were not likely to result in a noteworthy addition to total U-boat strength, and the U-Boat Inspectorate, worried about gaps in production in 1918, complained to the army high command at the end of May that the Reichsmarineamt was reluctant to place new orders with the end of the war presumably in sight, fearing the financial effect of the large orders on peacetime estimates and the fleet plan. Shortages in labor, material, critical components, and submarine engines also continued to plague the work on submarines already under construction.11
This optimism about a quick end to the war did not last long, for on 2 June a conference between the various authorities concerned with the submarine war concluded that in the light of war experience and operational losses, everything that could be built in any possible way by 1 January 1919 ought to be put in hand right away “as the general outlook of the war gave no justification for any reduction in the most committed work on, improvements to, and increase in numbers of U-boats.”12 The immediate result at the end of June was an order for an additional 95 U-boats. These included 39 UC.III boats (UC.80 to UC.118), an improved version of the successful UC.II minelayers, 37 additional UB.III boats (UB.133 to UB.169), 9 800-ton Ms boats (U.164 to U.172), and 10 large U-cruisers (U.173 to U.182). The boats were all to be ready between the summer of 1918 and early 1919.
There was some doubt about fulfillment of the program, for what were termed “crippling” shortages of material and skilled labor continued. On 23 July Capelle asked the War Office that submarine construction be given priority over all other forms of production. The War Office would not go quite that far, designating submarine deliveries only “as of the utmost importance.” In August the Reichsmarineamt decreed that in private yards submarine and torpedo-boat construction should take preference over new capital ship construction, and new U-boat construction, with a few exceptions, should even take preference over new torpedo-boat construction.13 This meant that the two powerful battleships Sachsen and Württemberg, armed with eight 38-cm guns and already launched, would never enter service. The same was true of the recently launched 35-cm-gun battle cruiser Mackensen and three of
her sister ships, already laid down. The Germans also had laid down the even more powerful battle cruiser Ersatz Yorck, armed with 38-cm guns, and planned another two of the same type.14 These, given the experience of Jutland, would have been formidable opponents, and their potential certainly worried the British. They were all sacrificed for submarine construction—yet another striking example of how the nature of the war at sea had changed.
THE PEAK OF GERMAN SUCCESS
The German blockade of the British Isles, the so-called Sperrgebiet, or “prohibited area,” might be described as a rectangle with cut corners. It ran from 20 miles from the Dutch coast to the Terschelling light vessel, then north to Utsire off the Norwegian coast, and then northwest to 62° N at its most northerly point, dipping to 3 miles south of the Danish-owned Faeroe Islands. It reached its most westerly point at 20° W before angling back to the Continent 20 miles off Cape Finisterre and then extending 20 miles off the neutral Spanish coast to the French frontier. There was also a prohibited zone in the Arctic Ocean, notably the approaches to Archangel and the Kola Peninsula. The Germans declared the waters in the Sperrgebiet closed to traffic, and that all neutral ships entering them would do so at their own risk. The Germans offered to permit one American steamer per week to proceed to Falmouth, provided its hull was marked with prominent red and white vertical stripes and it flew red-and-white-checked flags at each masthead. A daily Dutch paddle steamer with the same markings could also sail between Flushing and Harwich.15
The entire Mediterranean was also a Sperrgebiet, except for the area west of a line running southeast from near the mouth of the Rhône to a point approximately 60 miles off the French North African coast. There was also a 20-mile-wide corridor running through the Mediterranean to Cape Matapan and Greek territorial waters. Unarmed neutral vessels were allowed in these waters, although subject to prize rules. The exceptions catered to the maritime needs of neutral Spain and then-neutral Greece. The Germans eliminated the corridor in November 1917.16
The Germans soon paid the diplomatic price for their 1 February resumption of unrestricted submarine warfare. President Wilson of the United States felt mere diplomatic protests would no longer suffice, and on 3 February the United States severed relations with Germany. The president was still not convinced war was a foregone conclusion, but German action served to make it inevitable. At the end of February, the president learned of the Zimmermann telegram. This proposal by the German foreign secretary for a German-Mexican and possibly German-Japanese alliance in the event of war with the United States seemed to furnish further proof of Germany’s aggressive intentions. Its interception and disclosure were handled in a masterful fashion by British Intelligence. The inevitable sinkings by submarines also occurred. The Cunard liner Laconia (18,099 tons) was torpedoed and sunk by U.50 160 miles northwest of Fastnet on 25 February. The loss of life was relatively small among the 292 aboard, but there were three to four Americans among the twelve dead. There were also at least five American steamers sunk, including the Algonquin torpedoed without warning on 12 March. The German provocations were sufficient to bring the United States into the war.17 On 2 April Wilson asked Congress for a declaration of war. On 6 April the United States declared war on Germany—but not Austria-Hungary—and the same day seized German ships interned in American ports.18 The primary question now was whether the German naval and military leaders were correct in their assumption that it would not really matter and that the war would be over before American power could have any significant effect on events.
The priority given by the Germans to submarine construction in 1917 reflects the results of the unrestricted submarine campaign. At first it seemed all the Germans might have hoped for, even if by late spring it was evident the British might not succumb as fast as the Admiralstab’s U-boat enthusiasts had predicted. The losses inflicted by submarines rose from 328,391 tons in January to 520,412 tons in February, 564,497 tons in March, and a staggering 860,334 tons in April. April 1917 represented the peak of German success in the submarine campaign, for Allied losses fell to 616,316 tons in May. They went up somewhat to 696,725 tons in June, but would never again reach the April total.19 The “exchange rate” went from 53 in February to 74 in March to an astonishing 167 in April. In February, March, and April the Germans lost only nine submarines; two of them succumbed to their own mines rather than British countermeasures. Three months of unrestricted submarine warfare had reduced the world’s tonnage by more than two million tons, nearly 1.25 million tons British. The annual wastage of oceangoing tonnage was nearly 23 percent per year, rising to more than 50 percent per year in the last fortnight of April. The chance of a vessel safely completing a round voyage from the British Isles to a port beyond Gibraltar was now only one in four. The tonnage added through new construction or by transfer from foreign flags was simply insignificant in the face of these losses, and if they had continued at that rate, the British would have been compelled to make peace by November.20 As Henry Newbolt admitted in the official history, “Everything, indeed, combined to show that the Allies were really in sight of disaster.”21
The Germans also succeeded at first in their goal of terrorizing neutral shipping. British, Allied, and neutral ports were filled with neutral ships whose owners ordered them not to sail, and for a few weeks there was a general paralysis of neutral shipping. The British countered the crisis with ruthless measures of their own. They detained all neutral vessels in British ports and permitted them to sail for another Allied port only if they had received assurances they would not be laid up or diverted to a neutral port. Vessels trading with a neutral port were released only if they arranged to return with an approved cargo to a British or Allied port. Finally, in dealing with Dutch or Scandinavian ships, the British followed the so-called ship-for-ship policy in which vessels were allowed to sail only on the arrival in a British port of a similar vessel of the same flag.22
The intense British pressure on neutral ships to continue trading with British or Allied ports was of little use if the ships were sunk. The German onslaught was now overwhelming the British system for the defense of trade, which was exposed as totally inadequate. Troopships had been specially escorted or convoyed since the beginning of the war. Commencing in early March 1917, ships carrying cargo termed “of national importance” were given special routes through one of three triangles that had their apexes at Falmouth, Queenstown, and Buncrana. The ships were ordered to enter the base line of the triangle at a designated degree of longitude and relied for protection within the triangle on patrolling destroyers, sloops, and trawlers. The method was far from perfect; there were only about 20 ships to patrol the approximately 10,000 square miles of each triangle. The loss rate was high; from March to June 1917,63, or 7 percent, of the 890 ships routed in this manner were sunk, and in June the loss rate was a disturbing 11 percent.23 For the great majority of their ordinary shipping the British relied on a system of dispersion and patrolled lanes along coastal routes, which they considered “had sufficed” in 1915 and 1916. Steamers left ports at dusk and made port at dawn, followed dispersed routes far from the main trade routes, and crossed dangerous points in the hours of darkness. Every steamer received its orders from a specially appointed naval officer, and when the number of patrol craft in service had increased to a sufficient point, were directed to follow certain well-defined and closely patrolled routes that, whenever possible, were close to the shore. The Admiralty would act on intelligence of U-boat activity, anticipate the U-boat’s future movements, and divert trade to alternate routes. When all routes appeared to be threatened, the Admiralty suspended all traffic until the submarine had been destroyed or changed its area of operations.
There were flaws in the system; for example, owing to the requirements of secrecy, local commands did not always have the latest intelligence available from intercepts. Ships could be diverted only as they left port, and there was no method of controlling them while they were at sea. Inbound ships on the approach routes would be
acting on even older intelligence. Furthermore, while the suspension of traffic might have saved ships from being sunk, it also had the effect of enforcing the German blockade.24 The very detailed technical history produced by the Admiralty after the war made a significant point: “It is important to realize that the Routing System was not an alternative to direct protection, whether by patrols or convoy, but an auxiliary to such methods; when such methods were not available, owing to lack of ships, the Routing System could only hope to act as a palliative, and could never be a substitute for proper defensive methods.”25 Finally, there was another fatal flaw in any system of dispersion. However effective dispersion might have been, there were invariably certain focal points where approach and departure routes converged, and here submarines could count on finding attractive targets.
A Naval History of World War I Page 59