In warfare, a theatre or theater is an area where there are many battles. Theatres are bordered by peaceful areas.
Some wars are fought in one theatre. Many wars, for example the Seven Years' War have been fought in many different theatres. There were many theatres in World War I and World War II. The Napoleonic wars were the first multi-theatre war in modern times. The use of the word "theatre" for war was first seen in the book "On War" by Carl von Clausewitz.
Theater of operations
A Theater of operations (TO) is a sub-area within a theater of war. The boundary of a TO is defined by the commander who is orchestrating or providing support for specific combat operations within the TO. It means the territory, including adjoining sea areas and air space, in which a war was conducted.
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