Ever since the U.S. entered WW I in 1917, it had been sending divisions to fight in Europe in support of the major French or British units. However, later that year in 1917, President Woodrow Wilson sent the American Expeditionary Force (AEF), commanded and trained by General John J. Pershing.
The timing of its arrival was crucial to define the destiny of the war. This force came at a time when France and Britain's troops were weak and tired of the war. The major effect of its arrival is that the force helped counter the German forces, aided the Allies and helped to end the war, in which the allies gained the victory.
