Theater ( warfare ) In warfare , a theater ( US English ) or theatre is an area or place in which important military events occur or are progressing . A theater can include the entirety of the air , space , land and sea area that is or that may potentially become involved in war operations . Theater of war . In his book " On War " , Carl von Clausewitz defines the term as one that : " Denotes properly such a portion of the space over which war prevails as has its boundaries protected , and thus possesses a kind of independence . This protection may consist in fortresses , or important natural obstacles presented by the country , or even in its being separated by a considerable distance from the rest of the space embraced in the war . Such a portion is not a mere piece of the whole , but a small whole complete in itself ; and consequently it is more or less in such a condition that changes which take place at other points in the seat of war have only an indirect and no direct influence upon it . To give an adequate idea of this , we may suppose that on this portion an advance is made , whilst in another quarter a retreat is taking place , or that upon the one an army is acting defensively , whilst an offensive is being carried on upon the other . Such a clearly defined idea as this is not capable of universal application ; it is here used merely to indicate the line of distinction . " Theater of operations . " 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 . Theater of operations are divided into strategic directions or military regions depending whether it ' s a war or peace time . The United States Armed Forces split into Unified Combatant Commands ( regions ) that are assigned to a particular theater of military operations . Strategic direction is a group of armies also known as task ( field ) forces or battlegroups . Also in the US Armed Forces the term of strategic is often associated with missile command ( troops ) dropping word missile out of use such as the United States Strategic Command . However it is an important strategic command that could be effectively deployed in any theater of military operations . A strategic command or direction in general essence would combine a number of tactical military formations or operational command . In modern military , a strategic command is better known as a combat command that may be a combination of army groups . Soviet and Russian Armed Forces . For example a large geographic subdivision used by the Soviet and Russian Armed Forces to classify the continental geographic territories with their bordering maritime areas , islands , adjacent coasts and airspace . The division of large continental and maritime areas assists in determining the limits within which the plans for operation of strategic military groups of forces are developed , allowing conduct of military operation s on specific significant strategic directions known as fronts which were named in accordance to their theater of operations , for example Southwestern Front ( Russian Empire ) , 1st Ukrainian Front , Northern Front ( Soviet Union ) . In a peacetime due to loss of a strategic direction fronts were transformed into military regions ( districts ) responsible for an assigned section of operations . The Russian term is , " teatr voennykh deistvii " , abbreviated , " TVD " . United States . 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 control . Images and diagrams . Clicking onto image / diagram creates enlargement .