Military doctrine is a level of military planning between national strategy and unit-level tactics, techniques, and procedures. It provides a shared way of thinking about military problems, but does not direct how military problems will be solved. It does not provide specific steps to solve a problem, nor does it direct a commander to take any action. Commanders are always expected to exercise their own judgment in carrying out their missions.
Doctrine may be shared among the armed services of a nation as well as be specific to a branch. In addition, doctrine may be shared between several nations.
In general, doctrinal documents state:
A nation’s national military objectives
The general mission of the armed service or branch (“who we are”)
General concepts of how this service or branch shall perform its mission (“what we do”)
Concerns and cautions in carrying out this mission (“how we should do it”)
Historical examples (“how we did it in the past”)
Military doctrine changes, or should change, as the nature of warfare and the specific threat to a nation changes.