Allied forces halt Germany advance into France during First Battle of the Marne
Archduke Francis Ferdinand is assassinated
Battle of Verdun ends with 555,000 French and 450,000 German casualties
Peace conference begins at Paris
Allied and German representatives sign Treaty of Versailles. The U.S. state sign the Treaty of Guaranty, pledging to defend France in the case of an unprovoked attack by Germany
United States Senate fails to ratify Treaty of Versailles
Treaty of Versailles takes effect
United States Senate fails to ratify Treaty of Versailles for second time
