World War I was an international conflict that in 1914 embroiled most of the nations of Europe along with Russia, the United States, the Middle East, and other regions. The war pitted the Central Powers - mainly Germany, Austria-Hungary, and the Ottoman Empire - against the Allies - mainly France, Great Britain, Russia, Italy, Japan, and from 1917, the United States. It ended with the defeat of the Central Powers. The war was virtually unprecented in the slaughter, carnage, and destruction it caused.