XIII.

The United States Enters World War I

Although the United States remained neutral until three years into the war, it provided Britain with crucial military supplies. United States relations with Germany worsened in 1915, when a German submarine sank the British passenger liner Lusitania, killing 1,198 people, including 128 Americans. In 1917 Germany concluded that engaging the United States in the war might be less harmful than allowing it to trade freely with Britain. Germany declared unrestricted submarine warfare. Wilson realized that participation in the war was now inevitable and that entry would give the United States a prominent role in shaping the peace process after the war’s end. Wilson asked for a declaration of war, which Congress granted on April 6, 1917.

Unprepared, the United States was slow to make a significant military contribution in the war but succeeded in swiftly reopening essential supply lines. Not until the last months of the fighting did the doughboys, as the U.S. soldiers were called, become decisive in the final land offensive that defeated Germany. The war effort resulted in an enormous increase in American military power. By the end of the war a selective service system, established just a year before in 1917, managed to induct 2.8 million men between the ages of 21 and 35 into the military. With a force of about five million, the nation’s fighting manpower had increased nearly twenty-fold since the beginning of the war. The Spanish-American War had established an international foothold for the United States. World War I raised it to another tier.