The Allies and the Axis

The two opposing sides in the Great War were the Allies and the Axis. The Allies were composed of the following countries: The British, the French, the Russians, the Italians, the Serbians,  and the Japanese. The Axis, otherwise known as the Central Powers, were composed of the following countries: the Austro-Hungarians, the Germans, the Ottomans, the Bulgarians. These are just the major factions of both sides of the war, there were many more that are not listed here. 

Sources:

http://en.wikipedia.org/wiki/Allies_of_World_War_I

http://www.britannica.com/EBchecked/topic/16380/Allied-Powers

https://www.mtholyoke.edu/~raina20s/ww1/play.html

http://www.britannica.com/EBchecked/topic/102591/Central-Powers