In warfare, a theater or theatre is normally used to define a specific geographic area within which armed conflict occurs. A war would have to occur over a large portion of the globe in order to be considered to be large enough to have separate theaters, and the term is not used in the singular. Typically, each theater would be distinct and separate from other theaters. Very often, the delineation occurs along continental boundaries or in separate oceans. Typically, in order to be considered multiple theaters in a single conflict, at least one of the nations involved must be participating in multiple theaters; without this, each area is considered a separate war. For other uses of War, see War (disambiguation). ... Continental is: genitive case of continent e. ... Ocean (from Okeanos, a Greek god of sea and water; Greek ωκεανός) covers almost three quarters (71%) of the surface of the Earth. ...

The best (but not first) example of a war with several large and distinct theaters is World War II. This war had at least three separate theaters: European, Pacific, and African, though the latter is considered by some military historians to be an adjunct of the European Theater. Mushroom cloud from the nuclear explosion over Nagasaki rising 18 km into the air. ... German Führer Adolf Hitler Preceding events Main article: Events preceding World War II in Europe Main article: Causes of World War II Germany was in debt after World War I, due to the Great Depression and the forced payments to the victors of World War I. Germans wanted a leader... The Pacific War, which is known in Japan as the Greater East Asia War and in China as the War of Resistance against Japanese Aggression (kang-Ri zhanzheng, literally Resist Japan War), occurred in the Pacific Ocean, its islands, and in Asia. ... The battle in the North African desert during World War II from 1940-1943. ...

An American World War II theater of operations

Chart 12.- Typical organization of a theater of operations as envisaged by War Department Doctrine, 1940

An American theater of operations was an administrative term for a theater which had both an operational and an administrative command. For example in the European Theater of Operations US forces were under the joint allied operation command of SHAEF and the administrative command of the American ETOUSA; but in the China Burma India Theater American forces only had an administrative command as the operational command of ground troops was (theoretically) through the British 11th Army Group which reported to the joint allied command SEAC. The European Theater of Operations, or ETO, was the term used by the United States in World War II to refer to most United States military activity in Europe north of the Mediterranean coast. ... Supreme Headquarters Allied Expeditionary Force (abbreviated as SHAEF), was the command headquarters of the commander of Allied forces in North West Europe in 1944 and 1945. ... China Burma India Theater (CBI) was the name used by the United States Army for its forces in China, Burma, India during World War II. Well_known US units in this theater included the Flying Tigers, transport and bomber units flying the Hump, the engineers who built Ledo Road, and Merrill... The British 11th Army Group was the main British Army force in Southeast Asia. ... This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...

The term "theater of operations" was defined in the [American] field manuals as the land and sea areas to be invaded or defended, including areas necessary for administrative activities incident to the military operations (chart 12). In accordance with the experience of World War I, it was usually conceived of as a large land mass over which continuous operations would take place and was divided into two chief areas-the combat zone, or the area of active fighting, and the communications zone, or area required for administration of the theater. As the armies advanced, both these zones and the areas into which they were divided would shift forward to new geographic areas of control¹.

References

1. Chapter VII: Prewar Army Doctrine for Theater (http://history.amedd.army.mil/booksdocs/wwii/orgadmin/org_admin_wwii_chpt7.htm)