World War I: The U.S. ambassador Walter Hines Page to the United Kingdom is given the Zimmermann Telegram, in which Germany pledges to ensure the return of New Mexico, Texas, and Arizona to Mexico if Mexico declares war on the United States.

World War I, or the First World War, also known as the Great War, was a global conflict between two coalitions: the Allies and the Central Powers. Major theatres of war included Europe and the Middle East, and well as parts of Africa and the Asia-Pacific. One of the deadliest conflicts in history,…