Analyze the causes of World War I and the reasons the United States moved from neutrality to entry, including submarine warfare, the Zimmermann Telegram, and economic ties to the Allies (Louisiana Student Standards for Social Studies, US History Standard 3: Isolationism through the Great War).

What this topic is asking

World War I began in Europe in 1914, and for nearly three years the United States stayed out. Standard 3 (Isolationism through the Great War) wants you to analyze why the war started, why the United States was at first neutral, and what finally pushed it to enter in 1917. The decisive causes, submarine warfare, the Zimmermann Telegram, and economic ties to the Allies, are core LEAP content, often tested through a document, a cartoon, or a casualty chart.

Why the war began

The exam expects you to know the long-term causes, easily remembered as M-A-I-N:

American neutrality

When the war began, the United States declared its neutrality, in keeping with a long tradition, dating to George Washington's Farewell Address, of avoiding entanglement in European wars. Many Americans wanted no part of a distant conflict, and the country was home to immigrants from both sides. President Woodrow Wilson urged Americans to be neutral "in thought as well as in action," and in 1916 he won re-election partly on the slogan that he had "kept us out of war."

Why neutrality failed

Three pressures gradually pulled the United States toward the Allies.

• Unrestricted submarine warfare. Germany used U-boats (submarines) to sink ships without warning, trying to cut off supplies to Britain. In 1915 a U-boat sank the British liner Lusitania, killing nearly 1,200 people including 128 Americans, which outraged public opinion. Germany briefly pulled back, then resumed unrestricted submarine warfare in early 1917.
• The Zimmermann Telegram. In 1917 Britain intercepted and shared a secret German message, the Zimmermann Telegram, proposing that Mexico attack the United States in return for the recovery of territory it had lost in the 1840s. Its publication enraged Americans.
• Economic and cultural ties. American banks had lent heavily to the Allies, and American factories and farms sold them vast quantities of goods, so an Allied defeat threatened American interests. Cultural and language ties to Britain reinforced the lean toward the Allied side.

The decision for war

By early 1917 these pressures were overwhelming. After Germany resumed unrestricted submarine warfare and the Zimmermann Telegram became public, Wilson asked Congress for a declaration of war in April 1917, framing it as a fight to "make the world safe for democracy." The long American tradition of neutrality gave way, and the United States entered World War I (see the United States in World War I).