In the spring of 1917, the United States entered World War One. They joined the Allies- France, Britain, and Russia. Although many Americans, and Woodrow Wilson, did not want to enter the war, the situation eventually became undeniable, forcing the US to enter. When 128 Americans were killed by the sinking of the Lusitania from German U-boats, the US was angered. This, along with the Zimmerman telegraph, were major events that eventually caused America to join the war efforts.