Austria-Hungary declares war on Serbia, beginning World War I.
Austria-Hungary invades Russia
Allied forces halt German advance into France during First Battle of the Marne.
Allied forces land on the Gallipoli Peninsula of the Ottoman Empire.
Italy declares war on Austria-Hungary.
Germany begins the attack on Verdun.
Battle of Verdun ends with 550,000 French and 450,000 German casualties.
United States severs diplomatic relations with Germany.
The United States declares war on Germany.
American combat forces arrive in France.
Russia signs armistice with Germany.
Russia signs the Treaty of Brest-Litovsk with Germany.
Germany begins its final offensive of the war.
United States forces are victorious in the Battle of Cantigny, the first independent American operation.
American First Army attacks St. Mihiel salient.
Allied forces begin the attack at Meusse-Argonne, the final offensive of the war.
Germany signs the Armistice at Compiègne, ending World War I.
British and American forces enter Germany.
Peace conference begins at Paris.
Allied and German representatives sign treaty of Versailles. The United States signs treaty of guaranty, pledging to defend France in case of an unprovoked attack by Germany.
United States Senate fails to ratify Treaty of Versailles.
Treaty of Versailles takes effect.
United States signs separate treaties with Germany, Austria, and Hungary.