Having failed in 1916 to drive France from the war at the Battle of Verdun (on land), and the British at Jutland, and having, in turn, experienced the lengthy and damaging British attack in the Somme offensive (on land), in 1917 the Germans sought to force Britain from the war by resuming attempts to destroy its supply system. Unrestricted submarine warfare was resumed with one major consequence: the United States declared war against Germany. By the end of the year, the British managed to contain the German submarine threat by implementing a convoy system.
After the first fleet action in the dreadnought age, it is not surprising that there were a great number of technical and material considerations for the British to digest. One thing was evident: something had gone wrong with the battlecruisers, and a full investigation into their explosive demise was begun, resulting in strict anti-flash precautions being implemented, plus additional armor protection for all those ships still under construction. But urgent improvements were also required in the design of British shells, which had shown a distinct tendency to break up on impact, thus not causing the anticipated damage.
Despite their protestations of victory, the Germans were deeply chastened by some aspects of their Jutland experience. They knew they had done well, but they also knew how close they had come to annihilation. Whatever they would do next, it would not involve another fully fledged fleet confrontation. With successful fleet action ruled out, there seemed to be only one option left that promised any concrete results against their implacable enemy: submarine warfare. In October 1916 the Germans took their first cautious steps when they announced a return to restricted submarine warfare.
Germany announced a full resumption of unrestricted submarine warfare, not only in the war zone around the British Isles but also across the Mediterranean and shortly afterwards – most controversially – off the eastern coast of the United States. By this time the German U-boat fleet had swollen to over 150 modern submarines with ocean-going capability, although only around a third could be maintained out on patrol at the same time. But this proved enough to cause chaos to the essential sea lanes that fed and supplied Britain.
The Americans were incensed at the resumption of unrestricted submarine warfare and almost immediately severed diplomatic relations with Imperial Germany. Britain then fanned the flames of heightened American emotions by releasing the text of an ill-judged telegram from the State Secretary for Foreign Affairs, Arthur Zimmermann, dispatched in January 1917 to his Ambassador in Mexico, proposing an alliance between Mexico and Germany.
The American reaction was predictable. The United States declared war on Germany. The potential addition of several American dreadnoughts to the Grand Fleet merely emphasised the hopelessness of any ideas the High Seas Fleet might have of openly contesting British naval supremacy. But the Americans also brought the promise of an increased number of destroyers to fight the submarine war, while their booming shipbuilding industry would ultimately help replace lost Entente merchant tonnage.
For the British, victory in the prewar naval race was followed by victory in a wartime naval race that attracted, and has continued to attract, less attention. This is not surprising given that prewar building rates prefigured the outcome. Thus, the Germans were not able to fall back upon a margin of success in a large-scale shipbuilding program.
The Entente attempted to block U-boats in the Adriatic by establishing a barrier from Otranto in Italy across to the Dalmatian coast. Austro-Hungarian Captain Miklos Horthy planned a raid using three light cruisers, Novara, Helgoland, and Saida. Leaving the port of Cattaro at nightfall the cruisers reached the barrage and steamed along, blowing hapless Entente trawlers out of the water. Two accompanying destroyers sank an Italian munitions ship and its destroyer escort. The Entente subsequently abandoned night patrols by trawlers on the barrage.
As First Sea Lord at the Admiralty, John Jellicoe now became the man responsible for devising a solution to the U-boat menace in 1917. The on-off nature of the campaign had hitherto prevented the Admiralty from developing a coherent policy, so it was reliant on a fairly random combination of ad hoc measures, including endlessly patrolling warships, minefield barrage nets, the arming of more and more merchantmen and the unpleasant ruse de guerre of the Q-ship.
Although Jellicoe was correct in his belief that there was no single answer to the U-boat problem, at the same time it should have been evident that a very important component of any solution would be the introduction of a convoy system as employed by Britain in war since time immemorial. If introduced, such a system would at a stroke have cleared the seas of helpless victims. Even if a submarine had located a convoy, it would have been exposing itself to attack from the escort. Jellicoe feared that such a solution would create yet more problems.
The first experimental convoys proved a great success with none of the anticipated problems in station-keeping. But the introduction of a fully fledged convoy system was very slow, and shipping losses remained high throughout the summer of 1917. Jellicoe was still swamped by the real or imagined practical difficulties of the convoy system and so felt no urgency in addressing the implementation of the policy. Gradually the rate at which Entente shipping was being sunk began to fall in direct proportion to the number of ships travelling in convoy; at the same time the numbers of U-boats sunk began to rise.
Convoying owed much to American support. Although they lacked experience in anti-submarine warfare, the Americans deployed their fleet to help protect communication routes across the Atlantic. From May 1917, American warships took part in anti-submarine patrols in European waters, initially with six destroyers based in Queenstown in southern Ireland where Admiral Sir Lewis Bayley, the British commander, was a key figure in fostering Anglo-American cooperation.
More generally, convoying was an aspect of the Entente’s global direction of most of the world’s shipping, trade, and troop flows. The Allied Maritime Transport Council oversaw an impressive system of international cooperation at sea, allocating shipping resources so that they could be employed most efficiently. This was important as an aspect of economic warfare and also in lessening targets for German submarines.
Command and control was a key area of naval operations that benefited greatly from technological improvement. Developments with radio made it easier to retain detailed operational control. Directional wireless equipment aided location and navigation and was employed to hunt German submarines by triangulation, while radio transmissions changed from a spark method to a continuous wave system.
A dull pessimism began to color Jellicoe’s whole outlook on the war. This showed itself most clearly in a controversy over the measures required to destroy or render useless the German destroyer and submarine bases established in the Belgian ports of Zeebrugge and Ostend. At a meeting to discuss the matter, Jellicoe said that Britain would not have the necessary supplies to continue the war into 1918, an opinion shared by no one else. Douglas Haig, the commander of the BEF, reactated very strongly, condemning Jellicoe for his defeatist attitude.
Almost despite itself, the Admiralty had stumbled across the solution to the submarine crisis. Nevertheless, it was all too late, for Jellicoe would finally be dismissed by Geddes. The new First Sea Lord, Vice Admiral Sir Rosslyn Wemyss, had a far greater residual energy and was able to build on the sure foundations that Jellicoe had laid.
By the end of 1917 one of the great questions of the war had been answered: Britain would not after all be starved out. The failure of their submarines to achieve their ambitious targets resulted in a severe blow to German morale, and the German High Command realized that the war would not be won by the U-boats.