Answer:
The Entente vs the Central powers (Britain, France, Russia, Belgium, Romania, later Italy and Greece vs Germany, Italy, Austro-Hungary, later Ottoman empire)
Step-by-step explanation:
Italy was on both sides of the war because of promises of land by the entente or "the Allies" while it was originally on the side of the central powers previously by the alliance system that was going on about between the nations of Europe.