There were few efforts by any of the Central or Allied Powers to achieve a negotiated peace in the first two years of the war. By 1916 the most promising signs for peace seemed to exist only in the intentions of two statesmen in power—the German chancellor Bethmann and the U.S. president Woodrow Wilson. Wilson, having proclaimed the neutrality of the United States in August 1914, strove for the next two years to maintain it. (See the video.) Early in 1916 he sent his confidant, Colonel Edward M. House, to sound London and Paris about the possibility of U.S. mediation between the belligerents. House’s conversations with the British foreign secretary, Sir Edward Grey, resulted in the House–Grey Memorandum (February 22, 1916), declaring that the United States might enter the war if Germany rejected Wilson’s mediation but that Great Britain reserved the right to initiate U.S. mediatory action. By mid-1916, the imminent approach of the presidential election in the United States caused Wilson to suspend his moves for peace.

In Germany, meanwhile, Bethmann had succeeded, with difficulty, in postponing the declaration of unrestricted submarine warfare. Wilson, though he was reelected president on November 7, 1916, let another month pass without doing anything for peace, and during that period the German victory over Romania was taking place. Thus, while Bethmann lost patience with waiting for Wilson to act, the German military leaders came momentarily to think that Germany, from a position of strength, might now propose a peace acceptable to themselves. Having been constrained to agree with the militarists that, if his proposals were rejected by the Allies, unrestricted submarine warfare should be resumed, Bethmann was allowed to announce, on December 12, the terms of a German offer of peace—terms, however, that were militarily so far-reaching as to preclude the Allies’ acceptance of them. The main stumbling block was Germany’s insistence upon its annexation of Belgium and of the occupied portion of northeastern France.

On December 18, 1916, Wilson invited both belligerent camps to state their “war aims.” The Allies were secretly encouraged by the U.S. secretary of state to offer terms too sweeping for German acceptance; and the Germans, suspecting collusion between Wilson and the Allies, agreed in principle to the opening of negotiations but left their statement of December 12 practically unchanged and privately decided that Wilson should not actually take part in any negotiation that he might bring about. By mid-January 1917 the December overtures had ended.

Strangely enough, Wilson’s next appeal, a speech of January 22, 1917, preaching international conciliation and a “peace without victory,” elicited a confidential response from the British expressing readiness to accept his mediation. In the opposite camp, Austria-Hungary would likewise have listened readily to peace proposals, but Germany had already decided, on January 9, to declare unrestricted submarine warfare. Bethmann’s message restating Germany’s peace terms and inviting Wilson to persevere in his efforts was delivered on January 31 but was paradoxically accompanied by the announcement that unrestricted submarine warfare would begin the next day.

Wilson severed diplomatic relations between the United States and Germany on February 3, 1917, and asked Congress, on February 26, for power to arm merchantmen and to take all other measures to protect U.S. commerce. But American opinion was still not ready for war, and the Germans wisely abstained from attacks on U.S. shipping. What changed the tenor of public feeling was the publication of the Zimmermann Telegram.

Arthur Zimmermann had succeeded Jagow as Germany’s secretary of state for foreign affairs in November 1916; and in that same month the Mexican president, Venustiano Carranza, whose country’s relations with the United States had been critical since March, had virtually offered bases on the Mexican coast to the Germans for their submarines. Zimmermann on January 16, 1917, sent a coded telegram to his ambassador in Mexico instructing him to propose to the Mexican government that, if the United States should enter the war against Germany, Mexico should become Germany’s ally with a view to recovering Texas, New Mexico, and Arizona from the United States. Intercepted and decoded by the British Admiralty Intelligence, this message was communicated to Wilson on February 24. It was published in the U.S. press on March 1, and it immediately set off a nationwide demand for war against Germany.