World War I, World War II and the Depression Between

1. World War I (U.S. involvement 1917–1918)

In plain words: a chain of alliances dragged Europe into war in 1914; German submarine attacks and a secret plot pulled the U.S. in by 1917.

Causes in Europe: historians often use the letters MAIN:

• Militarism — building big armies and glorifying war;
• Alliances — promises to defend one another;
• Imperialism — competing for colonies;
• Nationalism — intense pride in one's own nation.

The spark was the assassination of Austria-Hungary's Archduke Franz Ferdinand in June 1914. The alliance system quickly pulled in the major powers. It worked like a schoolyard fight: one push, and every friend jumps in.

Look at the figure: these were the two sides.

U.S. entry: President Wilson declared neutrality. But American banks and businesses traded heavily with Britain and France. A German submarine sank the British liner Lusitania in 1915, killing 128 Americans. In early 1917, Germany resumed unrestricted submarine warfare — sinking ships without warning. Then the Zimmermann Telegram revealed a German proposal for Mexico to attack the United States. On April 2, 1917, Wilson asked Congress for war. He said, "The world must be made safe for democracy." Congress declared war on April 6.

Home front:

• The Selective Service Act (1917) drafted soldiers.
• Liberty Bonds paid for the war.
• The Espionage Act (1917) and Sedition Act (1918) punished criticism of the war.
• Many Black Southerners moved north for factory jobs in the Great Migration.

Outcome: fighting ended with the armistice of November 11, 1918. About 116,000 Americans died. Wilson's Fourteen Points called for open diplomacy and a League of Nations. But the U.S. Senate rejected the Treaty of Versailles (1919). The United States never joined the League. The treaty's harsh terms on Germany fed anger. That anger later helped Adolf Hitler rise.

2. The Great Depression and the New Deal (context)

In plain words: the economy crashed in 1929, millions lost their jobs, and President Roosevelt's New Deal tried to help.

The stock market crash of October 1929 began the Great Depression. Banks failed. Unemployment reached about 25% in 1933 — one in four workers had no job. Drought and dust storms in the Plains (the Dust Bowl) drove many farm families west.

Franklin D. Roosevelt took office in 1933. He declared, "the only thing we have to fear is fear itself." His New Deal followed the "three Rs":

Think of the three Rs like fixing a flooded house: bail out the water (relief), repair the damage (recovery), and fix the pipe so it doesn't happen again (reform).

Unemployment fell but stayed high. War production finally ended the Depression. Around the world, the Depression helped dictators and militarists gain power. Examples are Hitler in Germany (1933) and military leaders in Japan. Mussolini had ruled Italy since 1922. He grew more aggressive abroad.

3. From neutrality to war (1935–1941)

In plain words: dictators grabbed land in the 1930s; the U.S. tried to stay out, then helped Britain, and finally went to war after Pearl Harbor.

• 1930s: Japan invaded Manchuria (1931) and China (1937). Italy invaded Ethiopia (1935). Germany rebuilt its army and took Austria and part of Czechoslovakia (1938). Britain and France tried appeasement — giving in to avoid war — at Munich (1938).
• Neutrality Acts (1935–1937): Congress banned arms sales to nations at war. This reflected isolationist opinion, the wish to stay out of other nations' conflicts.
• September 1, 1939: Germany invaded Poland. Britain and France declared war. France fell in June 1940.
• 1940–1941: Roosevelt called for America to be the "great arsenal of democracy." The Lend-Lease Act (March 1941) sent weapons to Britain and later the Soviet Union. The Atlantic Charter (August 1941) set shared U.S.–British war aims.
• December 7, 1941: Japan attacked the U.S. naval base at Pearl Harbor, Hawaii. About 2,400 Americans were killed. Congress declared war on Japan the next day. Germany and Italy declared war on the U.S. on December 11.

Look at the figure: each step brought the U.S. closer to war.

4. The home front, key events and the Holocaust

In plain words: the whole country worked for the war, the Allies won key battles, and the Nazis murdered millions in the Holocaust.

Home front:

• Factories switched to making tanks, planes and ships. Unemployment fell to about 1%.
• Millions of women took industrial jobs ("Rosie the Riveter").
• Families bought war bonds and lived with rationing — limits on how much of a scarce item each person could buy.
• The Bracero Program (1942) brought Mexican workers to U.S. farms.
• Black Americans pursued the "Double V" campaign: victory over fascism abroad and racism at home.
• Under Executive Order 9066 (1942), about 120,000 Japanese Americans were forced into camps. In 1988 Congress apologized and paid reparations.

Key events:

The Holocaust: the Nazi regime murdered about six million Jews. It also murdered millions of others (Roma, disabled people, Poles, Soviet prisoners). Persecution grew step by step:

1. laws (Nuremberg Laws, 1935);
2. violence (Kristallnacht, 1938);
3. mass murder in death camps such as Auschwitz.

Allied troops liberated the camps in 1944–1945. Nazi leaders were tried at Nuremberg.

5. Outcomes of World War II

In plain words: the war cost tens of millions of lives and left the U.S. and the Soviet Union as the two strongest powers.

• Roughly 70–85 million people died worldwide. About 405,000 were American service members.
• The atomic bomb, developed in the secret Manhattan Project, began the nuclear age. Historians still debate Truman's decision to use it.
• The United Nations was founded in October 1945. This time the U.S. joined.
• The United States and the Soviet Union emerged as superpowers. This set the stage for the Cold War.
• At home, the GI Bill (1944) paid for veterans' college and home loans. It helped build a larger middle class.

Example: a GED question may ask why the U.S. joined the UN after refusing the League of Nations. The expected reasoning: Americans concluded that isolationism had failed. It had not prevented a second world war.