World War I started in 1914, after the assassination of Archduke Franz Ferdinand, and was on until 1918. During the conflict, Germany, Austria-Hungary, Bulgaria and the Ottoman Empire (the Central Powers) fought against Great Britain, France, Russia, Italy, Romania, Japan and the United States (the Allied Powers).
African countries were involved in the war except Ethiopia and the four small Spanish colonies that remained neutral in the war. Brazil was the only independent country in South America to support the Allied powers Germany and Austria Hungary. Other nations that joined the allied power includs Portugal, Japan, Greece, Romania, China and, towards the end of the war, various South American countries including Peru. Italy changed sides and joined the Allies in 1915. So many countries were involved in world war 1. This is not the entire list.
World War I began when a Bosnian Serb assassinated Archduke Franz Ferdinand of Austria. Germany was Serbia's ally, so was early into the war against Russia, whose allies were Austria, Poland, Hungary. Then other countries were drawn in as far as Japan, Australia and ultimately, the USA, which made the war global. Turkey, Britain, France, most of the European countries became involved early.
Russia, Britain and France were the main allies with Armenia, Belgium, Greece, Hejaz, Poland, Portugal, Romania, the Serb-Croat-Slovene state and Czechoslovakia then China and Thailand in support. the Central Powers, the enemy, included Bulgaria, the Ottoman Empire, Lithuania and Ukraine. This is not quite the entire list, a truly inclusive war that hopefully will never be repeated.