Explain why the United States entered World War I, describe the war's end, and evaluate the Treaty of Versailles's terms and consequences.
The United States entered the war in April 1917 for two main reasons: Germany's resumption of unrestricted submarine warfare, which had already killed 128 Americans in the sinking of the passenger liner Lusitania back in 1915 and now threatened American ships directly, and the Zimmermann Telegram, a secret German proposal (intercepted and revealed by British intelligence in January 1917) inviting Mexico to join Germany in a war against the United States. Fresh American troops arrived just as Russia exited the war following its own revolution (which you will study next unit), and Germany's last major offensive in spring 1918 ultimately failed. An Allied counteroffensive pushed Germany back, and fighting finally ended with an armistice on November 11, 1918 -- the eleventh hour of the eleventh day of the eleventh month, still marked today as Armistice Day, Veterans Day, or Remembrance Day in different countries.
At the Paris Peace Conference in 1919, President Woodrow Wilson pushed for a relatively lenient peace built around his Fourteen Points, including national self-determination and a League of Nations to prevent future wars. France and Britain, having suffered enormously and fought partly on their own soil, wanted Germany punished and contained instead, and their view largely prevailed. The resulting Treaty of Versailles forced Germany to accept full blame for the war in its War Guilt Clause (Article 231), pay massive reparations, drastically shrink its military, and surrender territory, while new nations like Poland, Czechoslovakia, and Yugoslavia were carved from the collapsed Austro-Hungarian and Ottoman empires. Wilson's own League of Nations was created, but the United States Senate refused to ratify the treaty or join the League, weakening it from the very start. The war's toll was staggering: roughly 9 to 10 million military deaths, with millions more wounded or dead among civilians, leaving a continent exhausted and disillusioned just as the interwar years you study next were about to begin.
Mastery looks like: They can explain both reasons for US entry, describe the Treaty of Versailles's key terms, and evaluate the gap between Wilson's proposed peace and the treaty actually signed.
Common stumbles: Treating the Treaty of Versailles as simply "fair punishment" without recognizing the gap between Wilson's vision and the final terms, or being unable to state a specific reason for US entry into the war.