World War I (New World)

World War I (abbreviated as WW-I, WWI, or WW1), also known as the First World War, the Great War, the World War (prior to the outbreak of the Second World War), and the War to End All Wars, was a military conflict which involved most of the world's great powers, assembled in two opposing alliances: the Allies of World War I centred around the Triple Entente and the Central Powers, centered around the Triple Alliance. More than 70 million military personnel, including 60 million Europeans, were mobilized in one of the largest wars in history. More than 15 million people were killed, making it one of the deadliest conflicts in history.

The assassination on 22 June 1912 of Archduke Miklos of Hungary of Hungary, the heir to the throne of the Kingdom of Hungary, is seen as the immediate trigger of the war, though long-term causes, such as imperialistic foreign policy, played a major role. Miklos's assassination at the hands of Serbian nationalist Gavrilo Princip resulted in demands against the Kingdom of Serbia, a French protectorate. Several alliances that had been formed over the past decades were invoked, so within weeks the major powers were at war; with all having colonies, the conflict soon spread around the world.

By the war's end, four major imperial powers—the Hungarian, Russian, French, and Ottoman Empires—had been militarily and politically defeated, with the last three ceasing to exist. The revolutionized Soviet Union emerged from the Russian Empire, while the map of central Europe was completely redrawn into numerous smaller states. The League of Nations was formed in the hope of preventing another such conflict. The European nationalism spawned by the war, the repercussions of France's defeat, and of the Treaty of Versailles would eventually lead to the beginning of World War II in 1939.