The Creation of the American Expeditionary Force (AEF)
The United States struggled for three years to stay out of the war and President Wilson ran on a peace platform in his 1916 reelection bid. His inaugural address on January 27, 1917 called for “Peace without Victory”, a clear way to peace for the Germans but they ignored it.
On January 31, 1917 Germany announced the resumption of unrestricted submarine warfare against the United States and Britain. On March 1, 1917 the American public learned from the Zimmerman Telegram, a coded German message intercepted by England and shared with the United States, that Germany had asked Mexico and Japan to join it in a war against the United States. To induce Mexico to do so, Germany offered to return to it the southeastern US states lost in the 1816-1847 war between Mexico and the United States. Pressure for the US to enter the war also built up as a strong financial lobby put weight behind those calling for America to join the fighting. American banking interests wanted the Allies to win, thereby insuring the collection of loans earlier extended to England and France.
At the time of entering the war, the United States did not possess a single organized combat division. It had, however, been engaged since 1916 in training 30,000 regular army people and 145,000 militia soldiers stationed along the Mexican Border in Texas, Arizona and New Mexico. They were there because of US concerns over civil war in Mexico. Combatants had crossed into New Mexico and killed American soldiers. There was little fighting for the out of date US army to do along that border but campaigning provided an introduction to modern logistics, communications and technology. The army experimented with the use of trucks, machine guns, mortars, aviation and poison gas, all while deployed over a large territory. More importantly, the army received advanced infantry training.
Commanded by Brigadier General John J. Pershing, the border troops became the nucleus of the US army that would fight in France as the American Expeditionary Forces. He was appointed its commander in May of 1917 and given almost dictatorial power and responsibility.