the nation that joined germany and austria-hungary after world war i began was
Central Powers It faced and was defeated by the Allied Powers that had formed around the Triple Entente. The Powers' origin was the alliance of Germany and Austria-Hungary in 1879. Despite having joined the alliance before, Italy refused to take part in World War I on the side of the Central Powers; the Ottoman Empire and Bulgaria did not join until after World War I had begun, even though the Ottoman Empire had retained close relations with both Germany and Austria-Hungary since the beginning of the 20th century.
American entry into World War I On December 7, 1917, the U.S. declared war on Austria-Hungary.[5][6]