Who are the major combatants in World War 1?

There were two groups of alliances in Europe. One was the Triple Alliance (also called the CentralPowers(Germany, Austria, Italy (who left to join the western powers). They were later joined by Turkey. The other major alliance was the Triple Entente (also called the Western Powers) o France, Russia and Britain. Portugal and Japan were allies of the Western Powers but took little part in the fighting. In the Balkans, Serbia was an ally of Russia, and Bulgaria sided with Germany. Hundreds and thousands of soldiers from the subcontinent were involved in the World War 1, many of them fighting for the Western Powers in France and Middle East. In 1917 the United States joined the Western Powers because German Submarines were sinking ships in the Atlantic with American citizens on board. In the same year, Russia withdrew from the war because of the Communist Revolution.