The Allied powers in World War I included Great Britain, France, the United States and Italy. The Allies included 25 nations in all.
The U.S. did not become an ally in the world until 1917. They joined on the grounds that Germany violated the U.S. neutrality agreement when they attacked the international shipped.The U.S. came in to the war as an associated power. They were not a direct ally to France and the United Kingdom. The U.S. claimed that this action was to avoid any foreign entanglements. Italy ended its alliance with central powers before joining the allies. Japan was considered to be an important ally as well. Belgium, Serbia, Greece and Montenegro and Romania were considered secondary allies. Although at one point Russia was apart of the allied forces, they withdrew and ended involvement in the war after signing the treaty of Brest Litovsk. After signing this treaty, they had a separate agreement of peace with the Central Powers. After the Russians withdrew from the war, the five Great Powers on the ally side of the war included the French Republic, British Empire, U.S., Italy and Japan. The first country to declare war on Germany was the United Kingdom on August 4th, 1914.