Questions about World War I

1.) "The Great War" began on July 28, 1914 when Austria-Hungary declared war on Serbia. The cause of the beginning of the world war was assassination of Franz Ferdinand by the Serbian Nationalist Gavrilo Princip. This war was fought between the Central Powers and the Allied Powers. Germany, Austria-Hungary, and the Ottoman Empire made up the Central Powers and Great Britain, France, Russia, Italy, and Japan made up the Allied Powers. 

2.) The U.S. entered the war on April 6, 1917 and joined the Allied Powers. A main reason America entered the war was the sinking of the Lusitania, a British Oceanliner, by the Germans,

3.) The Germans signed an armistice on November 11, 1918 that effectively ended the war. The Germans and the rest of the central powers were falling apart due to lack of resources and bad moral. Following the surrendering of many allies, Germany signed the armistice.

4.) The terms of the armistice were that the Germans had to leave all German-occupied territories on the Western Front within two weeks, Allied forces were to occupy the left bank of the Rhine whereas the right bank was established as a neutral zone. All treaties previously signed with Russia and Romania were annulled. The Germans had to give up most of their ammunition, aircraft, locomotives, and submarines. The United States did not ratify this treaty because they did not want to become part of the League of Nations. Other things such as hostility between countries and different ethnic groups in America not agreeing with the terms of the treaty played part in this.

5.) What made the countries divide into the powers that they did? Were these countries previously allies or just united by the war?