World War I included the Allies having conflict with the Central Powers.
The Allies of World War I , or Entente Powers , were the countries that opposed the Central Powers in the First World War . World War I . The war drew in all the world 's economic great powers , assembled in two opposing alliances : the Allies ( based on the Triple Entente of the Russian Empire , the French Third Republic , and the United Kingdom of Great Britain and Ireland ) versus the Central Powers of Germany and Austria-Hungary . Although Italy was a member of the Triple Alliance alongside Germany and Austria-Hungary , it did not join the Central Powers , as Austria-Hungary had taken the offensive against the terms of the alliance . These alliances were reorganised and expanded as more nations entered the war : Italy , Japan and the United States joined the Allies , while the Ottoman Empire and Bulgaria joined the Central Powers .