1. U.S. Enters the War
1917

2. U.S. in 1914
“The effect of the war upon the United States will depend upon what American citizens say and do. Every man who really loves America will act and speak in the true spirit of neutrality, which is the spirit of impartiality and fairness and friendliness to all concerned…” - President Woodrow Wilson

3. The War in 1917
1917 was a big year: Russia left the war; morale collapsed on both sides
Until 1917, the U.S. was still neutral, but it did unofficially side with the Allies
loaned millions of $$ and war materials to Allies
had cultural and historic ties to Allies
Allied propaganda against Germany swayed U.S. to side w/ Allies

5. Unrestricted Submarine Warfare
U.S. was under attack despite neutrality
German submarines attacked merchant and passenger ships carrying Americans
1915 – Sinking of the Lusitania – British ship carrying 128 Americans was torpedoed and sunk
Germany promised to stop,
hoping that the U.S. would not
join the Allies

7. "We intend to begin on the first of February unrestricted submarine warfare. We shall endeavor in spite of this to keep the United States of America neutral. In the event of this not succeeding, we make Mexico a proposal or alliance on the following basis: make war together, make peace together, generous financial support and an understanding on our part that Mexico is to reconquer the lost territory in Texas, New Mexico, and Arizona. The settlement in detail is left to you. You will inform the President of the above most secretly as soon as the outbreak of war with the United States of America is certain and add the suggestion that he should, on his own initiative, invite Japan to immediate adherence and at the same time mediate between Japan and ourselves. Please call the President's attention to the fact that the ruthless employment of our submarines now offers the prospect of compelling England in a few months to make peace."
Signed, ZIMMERMANN.

14. Wilson’s War Message, April 1917
"The world must be made safe for democracy. Its peace must be planted upon the tested foundations of political liberty. We have no selfish ends to serve. We desire no conquest, no dominion. We seek no indemnities for ourselves, no material compensation for the sacrifices we shall freely make." 

15. Impact U.S. entered the war on April 2, 1917
U.S. couldn’t provide many troops
But they did provide a morale boost to the Allies