Woodrow Wilson's campaign slogan was "He kept us out of war" when he ran for re-election in 1916 against Charles Evans Hughes. Five months after his re-election, he asked congress to declare war on the Central Powers.
The "Harlem Hellfighters" were the first all-black regiment in WWI. They earned their nickname from the Germans due to their toughness and the fact that they never lost a man through capture, lost a trench or a foot of ground to the enemy.
On March 3, 1918, the Bolshevik party which had come into power largely by playing on national discontent with the war, agreed to the Treaty of Brest-Litovsk, effectively pulling Russia out of World War I. The terms of the treaty were harsh, however, and Russia gave up vast territories to Germany including Finland, Poland, and the Ukraine.