American neutrality. When the war began, President Wilson quickly proclaimed the neutrality of the United States and called on the American people to be “impartial in thought as well as in action.” Absolute neutrality was difficult to achieve. German Americans tended to support the Central Powers, while Irish Americans had strong animosity toward Great Britain, and recent Jewish immigrants from Eastern Europe wanted a Russian defeat. On the other hand, the Allies, at least England and France, represented democracy to many Americans; the Allies had strong emotional support in the higher circles of government, especially in the State Department and the White House. Moreover, investors in the United States provided billions of dollars in loans to the Allies, and the balance of American trade with the warring countries was overwhelmingly in favor of Great Britain and France.

Although the United States objected to the British blockade in the North Sea, a much greater threat to American neutrality was Germany's use of unrestricted submarine warfare against shipping in the North Atlantic. In May 1915, Germany sunk the British oceanliner Lusitania , causing the loss of almost 1,200 lives, including 128 Americans. Although the United States strongly protested the incident (even though the ship was carrying contraband to Britain), there were several more sinkings before Germany, through the Sussex pledge (May 1916), agreed not to attack passenger ships without warning and to make provisions for the safety of noncombatants. The sinking of the Lusitania did raise questions about America's preparedness, however, and steps were taken to get the country ready for war. The National Defense Act provided for the immediate expansion of the regular Army to 175,000 men and a maximum of almost 250,000 troops, while the Naval Construction Act instituted a three‐year building program for the navy. The Council of National Defense was established to coordinate and mobilize industry, available natural resources, and labor in the event of hostilities with Germany.

In the 1916 presidential election, Wilson faced Republican candidate Charles Evans Hughes, a Supreme Court justice. The Progressive Party had nominated Theodore Roosevelt again, but he declined to run and threw his support to Hughes. Wilson campaigned as the peace candidate. Although the slogan “He kept us out of war” proved effective, the election was extremely close, with the vote in California for Wilson determining the outcome. The Democrats also kept control of the House of Representatives and the Senate. Before his inauguration, Wilson pressed the Allies and the Central Powers to clearly state their war aims and outlined his own ideas for “peace without victory” and an international organization to guarantee that peace.

These overtures became moot when Germany announced the resumption of unrestricted submarine warfare on all neutral or Allied shipping, effective February 1, 1917. The United States quickly broke diplomatic relations with Germany. In March, the State Department released the Zimmerman Telegram, a message intercepted from the German foreign minister to the German ambassador in Mexico that proposed an alliance with Mexico in the event of war with the United States. Mexico would reclaim Texas, New Mexico, and Arizona and was expected to persuade Japan to join the Central Powers. The publication of the message did little to enhance Germany in the eyes of Americans. March also witnessed a revolution in Russia that overthrew Tsar Nicholas II and put a democratic provisional government into power. The events in Russia were significant. When Wilson asked Congress for a declaration of war against Germany in April, largely on the basis of its submarine policy, he could do so with greater justification than before the Russian Revolution, arguing that the purpose of the war was to make the world “safe for democracy.”

The United States enters the war. The weakened condition of the Allied forces in the spring of 1917 made it clear that the United States would have to provide more troops than perhaps originally anticipated. In May, the Selective Service Act was passed, which made all men between the ages of 21 and 30 eligible for the draft; the age range was soon expanded to 18 to 45. Of the almost 5 million men who served in the military during World War I, 2.8 million were drafted. A total of 1.4 million Americans saw combat.

The Selective Service Act did not discriminate against African‐Americans, and many were drafted or volunteered. There was a widespread belief in the black community that military service would help break down prejudice and lead to political and economic gains. However, African‐Americans served in segregated units under white officers, and an overwhelming majority were relegated to menial jobs far behind the front lines.

Over the objections of Allied commanders, who wanted to use American troops to fill in their own lines, the American Expeditionary Force under General John J. Pershing fought as a distinct component on its own section of the front in eastern France. The first U.S. Army units landed in June 1917, but Americans did not see significant action until the German offensive in the spring of 1918. After initial successes, the Germans were pushed back in several major engagements in which American forces played a decisive role. The battles of Chateau‐Thierry and Belleau Wood (June 1918) blunted the German drive to the west, and the Second Battle of the Marne (July – August 1918) effectively ended the German threat to Paris. The first major American offensive of the war was the attack on the German units at St. Mihiel (September 1918), which was followed by the Meuse‐Argonne offensive – (September – November 1918). More than one million American soldiers fought in the Meuse‐Argonne and suffered a roughly 10 percent casualty rate, but the battle was the last confrontation of the war. With its military situation rapidly deteriorating, Germany asked for peace on the basis of Wilson's Fourteen Points, a statement of American war aims that the president had presented to Congress in January 1918. Great Britain and France reluctantly agreed to these terms with the provision that Germany pay reparations for the damages caused by the war. The armistice to end the fighting was signed on November 11, 1918.

By the end of the war, U.S. forces had suffered more than 53,000 combat deaths and over 200,000 wounded men. The total number of military deaths was considerably higher due to the worldwide influenza pandemic that struck the United States in 1918. But the end to the fighting on the Western front did not mean the quick repatriation of American soldiers from Europe. In November 1917, the Bolsheviks (Communists) came to power in Russia. In exchange for diplomatic and financial support for their administration, they signed a separate peace treaty with Germany (the Treaty of Brest‐Litovsk) in March 1918 and took Russia out of the war. Ostensibly to protect Allied supplies but more importantly to support the White anticommunist forces fighting the Red Army of the Bolsheviks, the United States and fourteen other countries sent troops to northern Russia in August 1918, and a smaller American force was sent to the Russian Far East soon after. The Allied intervention in Russia did not end until April 1920.

The home front during the war. To ensure support for the war effort, the Committee on Public Information (sometimes known as the Creel Committee after its head administrator, journalist George Creel) organized a propaganda campaign that portrayed Germans as barbarous Huns while stressing that Americans were fighting for democracy and freedom. Anti‐German sentiment reached ridiculous heights — many school districts across the country stopped teaching the German language, sauerkraut was renamed “liberty cabbage,” and German measles became “liberty measles.” The freedom to express dissent was also a casualty of the war. The Espionage Act of 1917 mandated imprisonment and fines for persons who aided the enemy or caused insubordination or disloyalty in the military. Newspapers, magazines, and other printed matter deemed as advocating treason were not allowed to be mailed. Under the Sedition Act (1918), it became a crime to make disparaging or profane comments against the government, flag, or the uniforms of the United States. Several thousand people were arrested under these laws, the constitutionality of which was upheld by the Supreme Court in Schenk v. United States (1919). The Court found that limitations on freedom of speech in wartime were legitimate if the speech constituted a “clear and present danger” to the public.

In addition to the Council of National Defense, a number of federal agencies were created to manage the economy. The Fuel Administration allocated supplies of petroleum and coal between industrial and domestic consumption and controlled the prices of these goods while the Railroad Administration coordinated rail traffic. The War Industries Board, under financier Bernard Baruch, converted America's factories to wartime production, directed the allocation of raw materials, and, when necessary, fixed prices. By promoting Victory Gardens and “Meatless Tuesdays,” the Food Administration, headed by future president Herbert Hoover, tried to increase agricultural production and limit civilian consumption. Following an unprecedented number of strikes in 1917, the National War Labor Board was created to arbitrate disputes between management and workers as well as to raise wages and shorten hours. Unions were permitted to organize and enter into collective bargaining for their members if they took a no‐strike pledge. In fact, union membership, particularly in the American Federation of Labor, grew significantly during the war.

The nature of the work force also changed. The severe labor shortage caused by the draft and the tapering off of immigration accelerated African‐American migration to northern industries from the South. Many young and single women also took on new jobs in the defense plants, although most lost those jobs when veterans returned from the war. The sense of patriotism that was at least partially responsible for bringing blacks and women into the factories in large numbers was also used to sell low‐interest government bonds, known as Liberty Bonds, to help finance the war. A sharp increase in taxes on profits, estates, and personal income increased revenues as well.