As part of the naval blockade of Germany, the British declared the North Sea a military area. From the outset, Theobald Bethmann Hollweg, the German Chancellor, was concerned about the possible reaction of neutral America. But the combination of press agitation and naval frustration overbore him, and on 4 February 1915 the Kaiser announced that the North Sea was a war zone and that all merchantmen, including neutral vessels, were liable to be sunk without warning. The US government immediately protested in the strongest terms.
In terms of propaganda and diplomatic effect, the sinking of the Lusitania off the Irish coast on 7 May 1915 had a strong impact. She was indubitably a British-owned vessel, and as it happened she was carrying munitions. But she was principally a passenger ship, and among the 1,201 who died were many women and children, including 128 American citizens. President Woodrow Wilson, an academic and a Democrat, had been president since 1913. For the moment he held back from war. In doing so he reflected the views of most of his fellow citizens. After the incident the Germans temporarily suspended U-boat warfare.
President Wilson still went further than his pacifist secretary of state, William Jennings Bryan, was prepared to accept. Bryan resigned when Wilson sent Germany a strong note demanding that it cease submarine warfare against unarmed merchantmen. It was a significant step: the sinking of the Lusitania had convinced his successor, Robert Lansing, that ultimately the United States would have to enter the war against Germany. Bryan’s resignation sprang directly from the dilemmas of neutrality. Although Bryan was wrong and the stronger notes to Germany did not lead to war, the crisis showed the difficulty American statesmen encountered in trying to find a neutral path.
The German army’s Supreme Command planned to remain on the defensive in the west in 1917, and endorsed a memorandum written on 22 December 1916 by the chief of the naval staff, Henning von Holtzendorff, arguing that unrestricted U-boat warfare could win the war by autumn 1917. Bethmann Hollweg remained very worried about the likely American response. Wilson’s policy was one of internationalism, but he recognized that its fulfilment might require the United States to take up arms. A German move to unrestricted submarine warfare was likely to be the precipitant to such a step.
German submarine captains, however, continued to attack merchant ships through the summer of 1915, usually warning the crews to evacuate, but not always. The policy varied with the personality and character of the submarine captain and with the particular situation. In August, Captain Rudolf Schneider of U-24 sank a British steamer without warning, the Arabic. Although most of the 433 passengers and crew were rescued, two Americans were among the 44 dead. World outrage mounted again, and this time the Kaiser issued explicit orders that not only should a liner be fully warned before being sunk, but that the submarine captain must observe that both crew and passengers safely boarded lifeboats before sinking the ship.
Germany advised the US government that armed merchantmen were to be treated as cruisers beginning on the 1st of March. This action came in response to the British use of Q ships in large numbers, to the use of neutral flags by British merchant ships, and to the open arming of merchant vessels. Realizing that Americans traveling on an armed merchant ship could easily be killed by either side, and that such an event could draw the United States into the conflict, members of Congress introduced congressional resolutions designed to preserve neutrality. The resolutions openly challenged Wilson’s policies. Again, Wilson reacted firmly, believing that no one, including ambassadors, secretaries of state and legislators, should infringe on his ability to set foreign policy.
Improved relations between the United States and Germany were threatened in the spring of 1916 over one more U-boat attack. A German U-boat torpedoed the Sussex, a French cross-channel passenger ship, and several Americans aboard were injured. The United States regarded the attack as a violation of the Arabic Pledge, but Germany claimed the submarine captain mistook Sussex for a minelayer. Wilson dismissed the minelayer story, and, in response to the sinking of Sussex, sent an ultimatum that unless Germany abandoned its method of submarine warfare, the United States would sever diplomatic relations.
Germany agreed to the US demands issued after the Sussex sinking but imposed a counter-condition that the United States compel the Entente to respect the rules of international law with regard to shipping, and in reference to mines, continuous voyage blockades, and rules of contraband. Traditionally, food had never been regarded as contraband, and shortages were affecting Germany. Wilson accepted the German response as a pledge but refused to accept the counter-condition. This so-called Sussex Pledge remained in effect, and German U-boat captains generally refrained from sinking passenger ships or American merchant ships over the next months.
The German chancellor resolved to appease potential American wrath by himself proposing peace. But the chancellor was so constrained by the army’s shopping list of war aims that his offer, when it was published, was meaningless. Realising that the Entente was likely to reject the German initiative, Wilson stepped in with one of his own. He invited the belligerents to state their terms. But the Entente did not want a peace set by America, and the Germans did not want a public debate on war aims, which was likely to divide the country internally.
On 8 January 1917 the navy and army presented a united front in an audience with the Kaiser, ‘who has suddenly come round to the idea that unrestricted U-boat warfare is now called for, and is definitely in favor of it even if the Chancellor is opposed to it.’ Georg von Müller, head of the naval cabinet, noted in his diary that ‘He voiced the very curious viewpoint that the U-boat war was a purely naval affair which did not concern the Chancellor in any way.’ Bethmann Hollweg was not even at the meeting, and when he was informed of the Kaiser’s decision he simply accepted it.
From the German perspective, the submarine blockade seemed to represent the best chance to bring the war to a successful end. A negotiated peace or a victory for the Entente would mean that Germany would have to pay indemnification, sacrifice territory, give up its colonies, and limit its arms. The Entente war goals, the German leadership believed, would reduce Germany to a second-rate power in Central Europe. A victory would leave Germany a major nation and world power, ranking as an equal to France and Britain.
With the announced blockade, most US ships stayed in port, although a few that had already departed began to arrive in European ports. The first two American ships to be destroyed under the new blockade were the steam-propelled freighter Housatonic and a schooner, the Lyman M. Law. In both cases, the submarine commander ensured that the crews evacuated the ships before sinking them, and no one died in these two sinkings.
It was now clear that the United States could not participate in world politics in any major way by staying out of the conflict. On 3 February 1917 America broke off diplomatic relations with Germany. Its reason for doing so was the danger to American shipping. The State Department notified Ambassador Johann von Bernstorff that the United States had severed diplomatic relations. In the expression of the day, the US government ‘handed his passports’ to Bernstorff.
Within sixteen days the US ambassador in London knew of a possible German threat to the United States itself: Germany had approached Mexico with an offer of alliance and an invitation to invade Texas. The foreign minister of Germany, Arthur Zimmermann, had decided that, in the event of war with the United States, Germany should seek new allies. Zimmermann used three different routes to send a message to the German ambassador in Washington regarding a potential alliance with Mexico. Room 40, the British Admiralty’s cryptanalysis department, intercepted all three. Although the Mexicans refused the German proposal, Wilson now had the motive to declare war on Germany.
The revelation, and Zimmermann’s own acceptance of its truth, persuaded the undecided in America that the US should intervene in the war. Wilson had little to offer in terms of immediate contribution. The first American troops landed in France in June 1917. However the first units to see any action, although on a small scale, were those of the 1st Division in October. It was not until 1918 that the American Expeditionary Force was able to bring a significant contribution to the war effort.
Through the rest of March 1917, the sinking of American ships by German submarines continued. A submarine sank the single-screw, three-masted steamship Algonquin. All members of the crew safely evacuated in lifeboats and landed in Penzance. What seemed to tip American public opinion and many newspaper editorialists in favor of war came in a single announcement of the sinking of three more American-registered and American-crewed ships: the City of Memphis, the Illinois, and the Vigilancia. In the case of the Vigilancia, 15 members of the crew died, including five Americans.
Wilson had little to offer in terms of immediate contribution. The first American troops landed in France in June 1917. It was not until 1918 that the American Expeditionary Force was able to offer a significant contribution to the war effort. The entry of the most powerful remaining neutral to the war removed any final constraint on the enforcement of blockade. America showed few of the reservations displayed by Britain, in dealing with the neutrals bordering on Germany. And that was where the United States’ military contribution was first felt.