Lesson 2: America Enters the War

Lesson Focus

Discover why the U.S. abandoned neutrality to enter World War I. This lesson explores Germany's provocations, America's rapid military mobilization, and how its forces helped turn the tide for the Allies.

People to Know

Woodrow Wilson, John J. Pershing

Learning Objectives

• Explain the events, including unrestricted submarine warfare and the Zimmermann Note, that pushed the United States into World War I.
• Detail how the U.S. military, through drafting and new tactics, helped the Allies achieve victory on land and at sea.
• Describe the experiences of African American soldiers, noting their contributions and the discrimination they faced in segregated units.
• Define key terms like 'doughboys' and 'armistice,' and explain phrases such as 'peace without victory' to understand the war's context.

President Wilson’s hope for a "peace without victory" was shattered by Germany’s desperate military situation.
In early 1917, Germany resumed unrestricted submarine warfare, breaking its Sussex Pledge. This, plus the shocking Zimmermann Note proposing a German-Mexican alliance, pushed America toward war.
After U-boats sank U.S. ships, Congress declared war. The U.S. mobilized quickly, using the Selective Service Act to draft an army of doughboys under General John J. Pershing, which proved decisive in achieving an armistice.

After declaring war in 1917, the U.S. had to build a large army from a small, unprepared force.
Following President Wilson’s call for a “universal obligation to serve,” Congress passed the Selective Service Act. This law required millions of men to register for the draft.
This rapid mobilization created a vast new army that boosted Allied morale. Note that this draft was the first used since the Civil War and was essential for raising a modern fighting force.

Over 370,000 African Americans served in the war, hoping to prove their patriotism.
However, they faced intense discrimination and were forced into segregated units. They were barred from the Marine Corps and limited to low-ranking roles in the Navy.
Despite this, Black soldiers fought with extreme bravery. Praised by General John J. Pershing, the 369th Infantry Regiment earned the French Croix de Guerre award for their gallantry in battle, demonstrating their crucial contribution.

By spring 1918, Germany launched a final offensive that threatened to break the Allied lines on the western front.
American soldiers, nicknamed doughboys, arrived to reinforce the Allies. Under General John J. Pershing, they helped halt the Germans at Château-Thierry and won a major victory at St. Mihiel.
The American counteroffensive shattered German defenses and morale, forcing Germany to seek an armistice and end the fighting on November 11, 1918.

German U-boats were sinking Allied merchant ships at a devastating rate, threatening to cut off Britain’s food supply.
To combat this, the U.S. Navy joined the British fleet. They used new depth charges to destroy submarines and protected vital supply ships by convoying them in armed groups.
The new tactics and technology successfully cut U-boat sinkings in half by late 1917, securing the Atlantic supply lines that were essential for the entire Allied war effort.