How is The Military Doctrine Formed?

In general definition, doctrine is the scientific, philosophic, political and religious theory. It is a set of spiritual systems that based on fixed principles. In military concept doctrine is defined at three levels, include; strategic, operational and tactical. Military doctrine can be one part of military idea or military philosophy, or result from military theories. Also it can propound in some military theories. Strategy determines that; in which way, we can shift from existing conditions to desire conditions and answer to this question: "What to do?" But doctrine is the answer for: "How to do?" Doctrine is the guiding lines and signs that must be regard for moving in this vector-strategy.