On the one hand, the major Allied powers of World War I, also known as the Entente powers, were Great Britain (and its Empire), France, and the Russian Empire, which had become Allies by the Treaty of London of 1914. Other nations became Allied powers by signing treaties with one or more of those powers. These were: Portugal, Japan and Italy. Finally, another group of nations were Associated powers. This was the case of the United States.
On the other hand, the Central Powers (since they were central European states) were Germany and its Empire, Austria-Hungary and the Ottoman Empire. Bulgaria joined this coalition in 1915.
