Today we reviewed the reasons for America's entry into WWI. The progress of WWI was significantly affected by Russia's withdrawal and the U.S. entry in the war. Initially, the US was strongly in favor of neutrality. President Wilson campaigned for reelection in 1916 on the slogan ''he kept us out of war.'' Yet, Germany's sinking of the Lusitania in May 1915 was a significant moment contributing to the US entry into WWI because one hundred U.S. civilians died in the event, leading to backlash against Germany. Another event turning the US public opinion against Germany was the January 1917 Zimmerman telegram, in which Germany promised Mexico territorial gains from the US if it joined the war on the side of Germany. The US joined the war in April 1917 after Germany resumed unrestricted submarine warfare, targeting neutral American ships. Russia fought WWI in alliance with France and Britain, yet it was losing against the German forces. The Russian economy and society was unprepared for a long war. In February 1917, the monarchy was overthrown, but the provisional republican government continued the war effort. Russian Communists (Bolsheviks), supported primarily by low-income factory workers, gained popularity, arguing for immediate peace with Germany. In November 1917, Bolsheviks took power in a military coup and, in March 1918, signed the Treaty with Germany, officially ending Russian participation in WWI.