Name the major countries of each of the two rival camps that clashed in 1914.

World War I began after the assassination of Franz Ferdinand, heir to the Austro-Hungarian throne, in Sarajevo on June 28, 1914. As a result, the Austro-Hungarian empire declared war on Serbia. Russia was part of the Serbian camp, while Germany joined the Austro-Hungarians. 
The Austro-Hungarians, Germans, and Ottomans formed the Central Powers, one of the two rival camps. On the other side were the Allied Powers, which included Serbia, Russia, Great Britain, France, Italy, Belgium, Japan, and other countries. In 1917, the United States also entered the war on the side of the Allies. Russia, whose monarch was deposed in 1917 during the Russian Revolution, withdrew from the war with the Treaty of Brest-Litovsk (signed in March of 1918). On November 11, 1918, the war ended with a victory for the Allies.