First event leading to US's enter into WWI:<span>Sinking of the Lusitania. May 7, 1915. American gov said stop unrestricted warfare. Germans said okay.
</span>Second event leading to US's enter to WWI:<span>Germany publicly announces using unrestricted sub warfare again. January 1917. America gives second warning. Germany ignores warning.
</span>Third event leading US's enter into WWI:<span>Zimmerman. Telegram sent to mexico by germany. Intercepted and decoded by great britain. translation given to US in Feb. 1917 America begins to mobilize for war.
</span>Fourth event leading to US's entrance in WWI:<span>April 1917. German U-boats sink four US merchant ships. America enters the war April 6 1917.</span>
