For war, least of all things, conforms to prescribed rules; it strikes out a path for itself when the moment comes.—Thucydides, Speech of the Corinthians, 432 B.C.
While the fundamental principles of war are neither very numerous nor complex, their application may be difficult and must not be limited by set rules. Departure from prescribed methods is at times necessary. —U. S. Army Field Regulations
It is now generally believed by all who have made a careful study of the military art, that, to secure unity of action, and, at the same time, to take advantage of favorable opportunities before it is too late, subordinates must act on their own initiative without orders from their superior in accordance with a general doctrine with which all are familiar.—Frost, “Night Torpedo Operations,” Naval Institute Proceedings, August, 1917