Ring of Steel

by Alexander Watson

  Even as the U-boats achieved their highest rate of sinking in April 1917, parts of the German naval hierarchy began to harbour doubts about the unrestricted campaign. The Marine Corps, the parent formation of the Flanders Submarine Flotilla, warned at the end of the month that despite the successes, there was no evidence that Britain would be defeated by August. Crews and boats were already being pushed to the limit and only the transfer of new vessels could bring greater destruction of shipping.58 The Marine Corps was clearly not alone in its scepticism, for in May the Leader of the High Sea Fleet’s U-boat forces, Commander Hermann Bauer, issued an order condemning all who expressed misgivings. The campaign’s feasibility was already statistically proven, he asserted. Intelligence reports all indicated that Britain was headed for catastrophe. What was needed now, he stressed, shifting from the material to the mystical, was ‘belief’. All faint-hearted thoughts should be quashed. ‘Only if we . . . carry within us and spread unshakeable belief in the natural necessity and, under the blessing of a higher power, the continuing decisive effect of our weapon can we achieve the goal that we have been set – the greatest ever demanded from a single arm – the saving of our Fatherland.’59

  The British were indeed in trouble; three months of unrestricted submarine warfare had cost them 1.9 million tons of shipping. They nonetheless proved adaptive and resilient. Their response to the U-boat threat was threefold. First, the Ministry of Food and the Food Production Department under the Board of Agriculture, both established at the turn of 1916–17, sought to reduce reliance on imports through cultivating and better managing domestic resources. Over 1916–18, strenuous efforts were made to raise home cereal production by turning 7.5 million acres of pasture over to arable farming. This led to a reduction in meat production, and so had only a limited impact on overall calories, but it was spectacularly successful in increasing the crucial staple foods: potato and wheat yields came to exceed those of 1904–13 by 40 per cent. Even more importantly, the British, like the Germans two years previously, stretched their flour stocks with husk and by mixing in other cereals, principally barley. The quality of British loaves never descended to the depths reached by German ‘War Bread’, however. Bread, despite the best efforts of the U-boats, was never rationed in the United Kingdom. Meat ration cards were issued only in February 1918.60 Captured German submariners observed the comparative abundance of food possessed by their enemy despondently. ‘One hardly notices anything of the war here, no cards of any kind, not even for bread,’ remarked the commander of U93, Edgar von Spiegel, in a letter to his wife after being taken prisoner by the British at the end of April 1917. ‘It is very sad, but it is true.’61

  Second, the British were ruthless in ensuring that merchant shipping remained available to them. The calculations underlying the unrestricted submarine campaign had been predicated in large part on its ability to scare neutral vessels from the high seas. The British countered with a little terrorism of their own: continental neutrals were warned that if they did prevent their ships from sailing, their own supplies would be cut. This was a wholly credible threat due to Britain’s control of coaling stations and access to the English Channel and North Sea. It was reinforced by the introduction of a ‘ship for ship’ policy: Dutch and Scandinavian ships were held hostage – to all intents and purposes – in British ports and were permitted to return home only when similar sized vessels trading under the same flag arrived to replace them. Other neutral vessels were released only if their captains promised to head to an Entente port or return with an approved cargo.62 Ship-building was also given new priority. The 53,000 tons that Britain produced each month in 1916 doubled to 102,000 tons in 1917. Its effort was dwarfed by that of the United States, which more than tripled the merchant tonnage at its disposal from 2.75 million tons in April 1917 to a colossal 9.5 million tons by September 1918. Even so, the Allies did suffer a shipping crisis in the war’s last year. Ironically, however, the cause was far less the U-boats than the new demand placed on the merchant fleets to convey to Europe and keep supplied millions of US soldiers. This was emphatically not the crisis that Henning von Holtzendorff had wanted or expected.63

  The third and, for the U-boat crews, most ominous response of the British to the unrestricted submarine campaign, and specifically to its initial success, was the introduction of convoys. Troopships and supplies had always been escorted across the Channel, and the tactic had also earlier been used successfully to protect merchant shipping on certain routes to Holland, Scandinavia and, in the case of the coal trade, France, but British admirals had baulked at any general introduction. A large convoy, they reasoned, would attract attention to itself by the smoke it produced and offer the U-boats more targets. Freighters could not be expected to keep formation. Moreover, the quantity of shipping that would need to be protected appeared so large as to make convoys unfeasible: statistics on arrivals and departures at British ports suggested that more than 300 ships would need escorting daily.64 In fact, these port statistics double-counted vessels by recording both arrivals and departures and also made no distinction between coastal traffic and large ocean-going freighters. When the U-boats’ successes forced a closer analysis, it turned out that rarely more than twenty cargo ships from across the Atlantic arrived daily at British ports. This was a far more manageable number, although the destroyers needed for the escorts were still in short supply. The Royal Navy estimated that it had forty available for convoy work, but required seventy-two. The ships were gradually provided by its US ally, the first six arriving in British waters in early May. By this point, the merchantmen’s horrendous losses the previous month had prompted the British War Cabinet to intervene and force a rethink in the Admiralty. The Prime Minister, David Lloyd George, pushed at the end of April for convoys to be trialled and on 10 May, the first group of sixteen ships under armed escort left Gibraltar. It proved a complete success.65

  The U-boat campaign was not instantly broken by the introduction of convoying. Indeed, as the figures for merchant tonnage sunk reveal (see Fig. 6), in June 1917 the submarine crews achieved their second highest score of the war, sinking nearly 670,000 tons of enemy and neutral merchant shipping. The Allies (as the Entente became with the entry of the United States into the war) needed time to implement the new system, and the US Navy Department was at first reluctant to commit large forces to the protection of merchantmen. While regular convoys sailed from Hampton Roads, Virginia, across the Atlantic from mid-June and were extended to other North American ports in the following weeks, only at the end of July did regular convoys begin leaving Gibraltar; and although some local escorting was introduced, not until mid-October was an organized convoy system developed in the Mediterranean.66 The U-boats also proved adept at locating chinks in the Allies’ new armour. The proportion of ships sunk on return voyages to America, which travelled unescorted until August 1917, rose over the summer. The U-cruisers attacked the weakly protected shipping around Madeira, the Azores and the Cape Verde islands, where another exclusion zone was declared in November. U-boats in the Mediterranean, helped by the sea’s narrowness and also by poor Allied coordination, remained more dangerous than those in northern waters.67 Most importantly, U-boats in the north switched from deep-sea operations to patrolling Britain’s coast, where there were still plenty of freighters steaming unprotected to the point at which a convoy was scheduled to gather or to a port for unloading, their convoys having dispersed. Whereas from February to July 1917 just 20 per cent of ships sunk were attacked within ten nautical miles of the coast, the proportion nearly tripled to 58 per cent in the second half of the year. Monthly sinkings, after falling precipitously from the heights recorded in spring, fluctuated between 270,000 and 450,000 tons in the autumn and winter, and from the start of 1918 until the war’s final months they stabilized at around 300,000 tons. While no longer sufficient to pose a mortal threat to Britain, this was far greater than at any point before October 1916 and a severe drain on Allied shipping.68

  Figur
e 6. Merchant shipping sunk by German U-boats (tonnage)

  Source: J. Schröder, Die U-Boote des Kaisers. Die Geschichte des deutschen U-Boot-Krieges gegen Großbritannien im Ersten Weltkrieg (Lauf a. d. Pegnitz, 2000), p. 430

  Nonetheless, if convoys did not eliminate the U-boat threat, they were the key factor in retarding it so significantly. The convoys not only emptied the seas of easy targets by concentrating and protecting shipping but they themselves proved unexpectedly difficult for submarines to locate. Between October and December 1917 just 39 of the 219 Atlantic convoys that sailed were even sighted by submarines. Their low detection rate was a consequence not just of the vastness of the seas but also of the British Admiralty’s ability to reroute the ships around danger. Warships, unlike most merchantmen, had powerful wirelesses, which could receive messages from London about the location of U-boats based on sightings or the interception of their radio communications. The Germans found no answer to this problem. The tactic used in the Second World War to intercept on land the wireless messages of Allied convoys and then direct boats onto targets was not practicable in 1917 and 1918 because the radios of U-boats were too primitive. A plan to equip one of the big U-cruisers with wireless and decryption personnel, and station it off the west coast of England to identify convoys’ locations and coordinate U-boat attacks, was rejected. Moreover, even when submarines spotted convoys, attacking them was difficult. A single U-boat lost the advantage of surprise already after its first shot and was not superior to heavily armed escorts. The tactic of grouping submarines into pairs or even packs was suggested, among others by the Kaiser, but an experiment in May 1918 showed that U-boat numbers were too few to allow for both cooperation and the guarding of all seaways. While the Allies had to put up with delays caused by collecting ships together and longer unloading times at ports, as groups of twenty, thirty or in one case even forty-seven ships arrived, the safety offered by the convoys outweighed all their disadvantages. Between August and October 1917 ships still sailing independently had a loss rate of 7.37 per cent; the rate in the convoys was just 0.58 per cent. The escorts also proved their value in protecting the liners and converted freighters carrying US troops across the Atlantic. Some 2,078,880 American soldiers were safely transported to Europe, mostly in 1918. Just 314 were lost at sea through U-boat action.69

  The convoys not only impeded the efforts of U-boats to sink ships but also forced them to fight under very unfavourable conditions. The offensive sweeps by warships, which had previously been the Royal Navy’s prime anti-submarine tactic, and which were still continued in the last years of the war, were highly ineffective because U-boats had no reason to engage and detection equipment was still in its infancy.70 Once convoys were introduced, however, the submarines had no choice but to confront escorting sloops and heavily armed destroyers: as the commander of UB52 observed ruefully, the patrols had been easy to evade, but with convoys ‘now every target met with has an attendant defender’.71 Improvements in Allied weaponry further increased the danger to submarines. The depth charges carried by escorts, dismissed by U-boat crews in 1916 as ‘firecrackers’, had just a year later been developed into powerful devices capable of sinking or forcing to the surface a submarine if they exploded within 30 metres. To be depth-charged was the naval equivalent of sheltering under an artillery bombardment; captured submariners described how sitting helplessly under depth-charge attack summoned a ‘feeling of oppression . . . very difficult to overcome’.72 When the U-boats turned increasingly to coastal traffic in order to find unescorted targets, this made them more vulnerable to interception, for once near land they came in range of aerial reconnaisance. As early as June 1917, submarines off England’s east coast were being gravely hampered by airship activity. By 1 January 1918 the British were deploying 100 airships, 23 aeroplanes and 291 seaplanes on anti-submarine duties. Aircraft destroyed at most four U-boats, but they provoked nervousness disproportionate to this success and by the summer of 1918 many submarines had returned to hunting further out to sea in order to avoid them.73 The new danger posed by convoy tactics and improved weaponry was reflected in the submarines’ loss rates: in 1917 twenty were sunk by enemy action during the first six months, but more than double that number, forty-three in total, during the second half of the year. Losses were even worse in 1918, amounting to 102 from all causes.74

  Mine-laying also made a significant but late contribution to the fight against German submarines. British mines were, for most of the war, extremely unreliable. One UC-boat commander, confident they would not explode, even scooped two up on a mission in October 1917 and had them made into punch bowls on his return home. Only when the British gave up trying to design their own contact mine and copied a proven German pattern did they begin to have success. By the turn of 1917–18, their new H2 mines were being laid in such numbers and proving so lethal that submarine crews had lost their nonchalance and were becoming very frightened.75 Thirty-four of the 178 U-boats sunk through enemy action during the war were accounted for by mines or combinations of mines and underwater nets. The ambition of British naval planners went far beyond destruction, however; they hoped to use mines to box in or at least impede the movement of the submarines. Efforts to confine German and Habsburg U-boats to their Adriatic bases by placing mines, nets and drifters in the Strait of Otranto, between the heel of Italy and Albania, failed. A megalomaniac US plan to block the entrance to the North Sea resulted in 70,263 mines being sown along a stretch of water 400 kilometres in length in the war’s last months. At a cost of 40 million dollars, this ‘Northern Barrage’ sunk at most seven submarines. However, the more manageable goal of closing off the Dover Strait was achieved. The first British attempt in December 1916 comprised an intricate combination of nets and minefields between Goodwin Sands and Dunkirk. It was quickly damaged by the Channel’s strong currents and proved totally useless: as many as thirty German U-boats crossed over it monthly to and from their hunting grounds further west. At the end of 1917 the British had a second try, this time laying a deeper minefield and posting trawlers with flares and searchlights to illuminate the surface of the water at night. The hope that U-boats attempting to creep across would be forced by the glare to dive into the minefield beneath was vindicated. On the very first night that the new system was trialled, UB56 was caught in the searchlights, dived, and was destroyed by a mine. Over the next five months, the new barrage accounted for a submarine on average every three weeks. Consequently, the U-boats again began to travel around Scotland to reach their hunting grounds, losing valuable time that in turn reduced the rate of merchant sinkings.76

  One of the gravest consequences of the drawn-out and increasingly unfavourable fighting was the dissipation of the ‘unshakeable belief’ that Hermann Bauer, Leader of Submarines, had urged upon his crews in May 1917. The sailors became exhausted: in the first seven months of the unrestricted campaign most spent over one-third of their time at sea and those in the Flanders Flotilla over 40 per cent.77 By November, men from U48 captured by the British were reportedly attributing ‘the recent increase in the number of losses . . . mainly to this system of “driving” the submarines all the time at top pressure’.78 The force also deskilled. Much has been made of the German navy’s complacency in not constructing sufficient submarines: none were ordered between September 1915 and May 1916, and those started afterwards were still being built when the war ended. Nonetheless, enough were completed in 1918 to keep the numbers reasonably stable, despite severe losses, at about 128 U-boats, the German force’s strength in March 1917.79 The real problem was finding and training crews and competent commanders for these new submarines. Reserve crews were said to be ‘nothing more than untrained recruits’ and veteran petty officers were increasingly scarce.80 Exhaustion, rising casualties and the influx of new, inexperienced sailors into the service lowered morale. In April 1918 British intelligence observed that ‘the recent heavy losses in submarines have made the crews extremely nervous’.81 Officers of the Flanders Flotilla s
tarted to consume noticeably more alcohol onshore and the formation was sardonically dubbed the ‘Drowning Command for ex-Merchant Service Officers’ – a reference to the merchant-fleet background of many of the reserve officers now commanding smaller German submarines.82