This depends upon:—
(1) The theatre of the war.
(2) The means at our disposal.
1. Theatre of the War.—Usually defined as "all the territory upon which the hostile parties may assail each other." This is insufficient. For an island power the theatre of war will always include sea areas. Truer definition: "geographical areas within which lie the ulterior objects of the war and the subordinate objects that lead up to them."
A "theatre of war" may contain several "theatres of operations."
2. Theatre of Operations.—Is generally used of the operations of one belligerent only.
An "operation" is any considerable strategical undertaking.
A "theatre of operations" is usually defined as embracing all the territory we seek to take possession of or to defend.
A truer definition is, "the area, whether of sea or land or both, within which the enemy must be overpowered before we can secure the object of the particular operation."
Consequently, since the nature of the war varies with the object, it may be defensive in one theatre of operations and offensive in another.