America’s policy of insisting on neutral rights while also trying to broker a peace resulted in tensions with both Berlin and London. U.S. President Woodrow Wilson repeatedly warned that he would not tolerate unrestricted submarine warfare, and the Germans repeatedly promised to stop. A proposal to Mexico to join the war against the Allies was exposed in February, bringing war closer. After further U-boat (German submarines) attacks on American merchant ships, Wilson requested that Congress declare war on Germany, which it did on April 6, 1917. The U.S. House of Representatives approved the war resolution 373-50, the U.S. Senate 82-6, with opposition coming mostly from German American districts. Wilson hoped war could be avoided with Austria-Hungary; however, when it kept its loyalty to Germany, the U.S. declared war on Austria-Hungary in December 1917.
Although the American contribution to the war was important, particularly in terms of the threat posed by an increasing U.S. infantry presence in Europe, the United States was never formally a member of the Allies, but an “Associated Power.” Significant numbers of fresh American troops arrived in Europe in the summer of 1918, and they started arriving at ten thousand per day.
Picture 1: Sinking of the RMS Lusitania
Germany miscalculated that it would be many more months before large numbers of American troops could be sent to Europe, and that, in any event, the U-boat offensive would prevent their arrival.
The United States Navy sent a battleship group to Scapa Flow to join with the British Grand Fleet, several destroyers to Queenstown, Ireland and several submarines to the Azores and to Bantry Bay, Ireland to help guard convoys. Several regiments of U.S. Marines were also dispatched to France. However, it would be some time before the United States would be able to contribute significant manpower to the Western and Italian Fronts.
Picture 2: African American unit, marching northwest of Verdun, 5th Nov. 1918
The British and French wanted the United States to send its infantry to reinforce their troops already on the battle lines, and not use scarce shipping to bring over supplies. Consequently, Americans primarily used British and French artillery, airplanes, and tanks. However, General John J. Pershing, American Expeditionary Force (AEF) commander, refused to break up American units to be used as reinforcements for British Empire and French units (though he did allow African American combat units to be used by the French). Pershing ordered the use of frontal assaults, which had been discarded by that time by British Empire and French commanders as too costly in lives of their troops. To the astonishment of the Allies, the dispirited Germans broke and ran when the Americans came running, and the AEF suffered the lowest casualty rate of any army on the Western Front, with most recorded deaths being attributed to disease.