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The American public was outraged, but still did not support declaring war against Germany.
The spark was the assassination in Bosnia of Archduke Ferdinand in June 1914, and war between the two alliances soon began. The secret promises among many countries to defend each other caused them to be pulled into the war, making this the first genuine world war in history.
Congress began to prepare for war. In 1916, it passed the National Defense Act, which was a military preparedness program that expanded the army, increased the size of the National Guard fourfold, and set up "ROTC" programs for college students to earn tuition in return for military service. It gave the president the power to mobilize the National Guard in the event of a national emergency such as war.
