America Enters WWI: From Neutrality to Decisive Intervention (1917–1918)

The United States didn't want World War I. It ended up deciding it. Here's how neutrality collapsed and 2 million doughboys tipped the balance.

1914–1916: Armed Neutrality

• Wilson: "Neutral in thought and deed"
• Trade with Allies booms (loans, munitions, grain)
• Germany protests — but US insists on neutral rights

Three Shocks That Broke Neutrality

1. Lusitania (May 1915): U-boat sinks British liner — 1,198 dead, 128 Americans. Outrage. Germany pledges restriction.
2. Zimmermann Telegram (Jan 1917): British intercept: Germany proposes Mexico alliance — "reconquer Texas, NM, AZ." Published March 1. Public fury.
3. Unrestricted Submarine Warfare (Feb 1917): Germany resumes sinking all ships in war zone. US merchant vessels hit. Wilson: "Property can be paid for; lives cannot."

April 6, 1917: War Declared

Congress votes 373–50 (House), 82–6 (Senate). "The world must be made safe for democracy."

US War Machine Spins Up

• AEF (American Expeditionary Forces): Gen. Pershing, 2M in France by Nov 1918
• Selective Service Act: 24M registered, 2.8M drafted
• Liberty Bonds: $21B raised — public finance as patriotism
• Industrial mobilization: War Industries Board, Railroad Administration, Food/Fuel Administrations

Impact: The Tipping Point

• Spring 1918: Germans' last offensive (Kaiserschlacht) — Americans hold at Cantigny, Belleau Wood, Château-Thierry
• Summer 1918: AEF independent — St. Mihiel, Meuse-Argonne (1.2M men, 47 days)
• Nov 11, 1918: Armistice. US casualties: 116,516 dead, 204,000 wounded

Aftermath: Isolationism's Irony

Wilson's 14 Points → League of Nations → US Senate rejects Treaty of Versailles. America retreats. But the world had changed: US as global creditor, military power, ideological force.

WWI made America a world power. The next war would make it the superpower.