The British decode the intercepted message and discover the German proposal for an alliance with Mexico against the United States.

The U.S. troops of the Punitive Expedition, after skirmishes with Carrancistas forces and successful diplomacy, withdraw from Mexico.

United States severs diplomatic relations with Germany. President Woodrow Wilson tells a joint session of Congress that Germany’s policy of unrestricted U-boat warfare poses an unacceptable threat to ...

The United States is informed of the German High Command order to resume unrestricted submarine warfare.

Germany’s foreign minister, Arthur Zimmermann, cables the coded proposal to Germany’s Ambassador in Washington D.C., Count Johann Henrich von Bernstorff. Because of severed transatlantic lines,...

A proposal of an alliance with Mexico is drafted by Hans Arthur von Kemnitz, a German foreign office official.

Having suspended attacks in 1916 to avoid U.S. entry into the war, German officials decide to re-engage in unrestricted submarine warfare against all ships.

After raids and increased public anger on both sides of the border, President Wilson and President Carranza convene a Joint High Commission in Connecticut to improve diplomatic relations between the...

Francisco "Pancho" Villa, a revolutionary formally backed by the U.S. government, and an army of guerrillas raids and razes the town of Columbus, New Mexico, leaving 19 Americans dead.