Since the beginning of World War I in 1914, the United States, under President Woodrow Wilson, had maintained strict neutrality, other than providing material assistance to the Allies. Even in May 1915, when a German submarine sank the British ocean liner Lusitania, killing 128 U.S. citizens out of a total 1,200 dead, the United States, though in uproar, remained neutral. In the autumn of 1916, Wilson was reelected after running largely on a platform of antiwar, pro-neutrality rhetoric.
By the time of Wilson’s reelection victory, the war had left millions dead, cities and economies in ruins, and no decisive victory in sight for any side. It seemed that the war might actually burn itself out. In November and December 1916, Wilson began a series of initiatives to broker a resolution, sending out diplomatic notes to the governments of every nation involved. Germany responded positively and went so far as to recommend opening immediate peace negotiations. France, however, responded by launching a renewed attack against the Germans in Verdun. British prime minister David Lloyd George rejected Wilson’s initiative directly.
In January 1917, Germany announced that it would lift all restrictions on submarine warfare starting on February 1. This declaration meant that German U-boat commanders were suddenly authorized to sink all ships that they believed to be providing aid of any sort to the Allies. Because the primary goal was to starve Britain into surrendering, the German effort would focus largely on ships crossing the Atlantic from the United States and Canada.
The first victim of this new policy was the American cargo ship Housatonic, which a German U-boat sank on February 3, 1917. In response, President Wilson broke off diplomatic relations with Germany the same day. The escalation was serious and turned out to be a major step toward the United States’ entry into the war.
In the meantime, other German mischief paved the road to war with the United States even more smoothly. In February 1917, British intelligence intercepted a telegram from Germany that they had intercepted in January. In the telegram, sent by German foreign minister Alfred Zimmermann to his ambassador in Mexico on January 16, Zimmermann instructed the ambassador to offer Mexico generous financial aid if it would ally itself with Germany against the United States. Furthermore, the telegram promised German support for Mexico in reconquering its lost territory in Texas, New Mexico, and Arizona.
On March 1, 1917, the text of the Zimmermann telegram appeared on the front pages of American newspapers, and in a heartbeat, American public opinion shifted in favor of entering the war.