Military doctrine is the expression of how military forces contribute to campaigns, major operations, battles, and engagements. A military doctrine outlines what military means should be used, how forces should be structured, where forces should be deployed, and the modes of cooperation between types of forces. "Joint doctrine" refers to the doctrines shared and aligned by multinational forces or joint service operations.
There are three broad categories of military doctrines: (1) Offensive doctrines aim to disarm an adversary, (2) Defensive doctrines aim to deny an adversary, and (3) Deterrent doctrines aim to punish an adversary. Different military doctrines have different implications for world politics. For example, offensive doctrines tend to lead to arms races and conflicts.
NATO's definition of doctrine, used unaltered by many member nations, is:
Fundamental principles by which the military forces guide their actions in support of objectives. It is authoritative but requires judgement in application.
In 1998 the Canadian Army stated:
Military doctrine is a formal expression of military knowledge and thought, that the army accepts as being relevant at a given time, which covers the nature of conflict, the preparation of the army for conflict, and the method of engaging in conflict to achieve success ... it is descriptive rather than prescriptive, requiring judgement in application. It does not establish dogma or provide a checklist of procedures, but is rather an authoritative guide, describing how the army thinks about fighting, not how to fight. As such it attempts to be definitive enough to guide military activity, yet versatile enough to accommodate a wide variety of situations.
A U.S. Air Force Air University staff study in 1948 defined military doctrine functionally as "those concepts, principles, policies, tactics, techniques, practices, and procedures which are essential to efficiency in organizing, training, equipping, and employing its tactical and service units".
A U.S.