World War
A world war is a military conflict affecting the majority of the world's countries. World wars usually span multiple continents, and are very bloody and destructive.
The term is usually used to refer to World War I (1914–1918) and World War II (1939–1945). Both wars involved some degree of participation from most of the world's existing countries, specially through the colonial empires of Great Britain, France, Germany, Italy and Japan, besides the United States and the Soviet Union.
Other wars in earlier periods that saw conflict across the world have been considered world wars by some, including the Seven Years' War (1756–1763; Winston Churchill called it "the first world war" in his A History of the English Speaking Peoples), the French Revolutionary Wars (1792–1802) and the Napoleonic Wars (1803–1815).
There is some disagreement on whether there have been any world wars since 1945. "World War III" was widely used to refer to a hypothetical nuclear war between the Soviet Union, the United States and their allies. "World War III" has also been used to refer to the Cold War (1945–1990) and to the War on Terrorism. "World War IV" was used by Professor Eliot Cohen to refer to the War on Terrorism. However, these designations are not widely used.
Since the conclusion of World War I, called "the war to end all wars," international organizations have been developed to prevent the outbreak of new wars. The League of Nations was established after World War I, and collapsed with the outbreak of World War II, after which the United Nations was formed.
