Serbs plotted to kill Archduke Franz Ferdinand ar Sarajevo parade good will tour, him and his wife were killed. The Austrians blamed the Servian government and threatened war if nothing was done to prosecute the killers.
WWI begins & US reaction
Austria and Germany threatened Servia and angered it s powerful allie Russia. They were ready for war. France sided with Russia and Britain was eventually sucked in. Most Americans were against Germany but they were supposed to stay neutral in deed and in thought.
Sinking of Lusitania
Germans sunk 4200 cases of American Ammunition, but at the cost of 128 innocent Americans. The American public was outraged and demanded action.
Two were Americans killed in a British merchant ship. The US made Germany pledge not to sink any unarmed merchant ships.
Pancho Villa raids New Mexico
Pancho Villas men hauled sixteen young American mining engineers and killed them. It pushed Woodrow Wilson to subdue him. Pacho Villa was probaly funded by the Germans.
"He kept us out of war"
Woodrow Wilson's 1916 campaign slogan which meant that the United States had not been pulled into World War I under Wilson (yet).
With another sinking of a passenger liner Germany again agreed to not sink any unarmed ships with the condition that the US would persuade the allies to modify the blockade.
Resumption of unrestricted submarine warfare
In an attempt to crush the allies Germany announced that it would now attack any ship regardless if it was armed or unarmed. Germany hoped to finish the war before the US could enter the war.
Arthur Zimmermann secretly proposed a German-Mexican alliance tempting anti-yankee Mexico with veiled promises of recovering Texas, New Mexico, and Arizona. This angered the Americans.
Since the Russians were out of the war due to their revolution, America could now join the war with claims of fighting for democracy.