(1) For securing command of sea areas,
(2) In sea areas not under command, and
(3) In sea areas under command.
On the basis of this classification, specific operations, broadly considered, appear to be limited in number. As to classification (1), applicable operations are: to destroy the enemy naval forces, to contain them, or to divert them. For (2), applicable operations are: to raid, to make war against enemy trade, to attack or defend naval lines of communication, and to conduct amphibious warfare requiring overseas movement. For (3), applicable operations are: to blockade trade, to defend own coastal and critical areas, to safeguard expeditions against enemy territory, and to carry out offensive operations against enemy coastal objectives.
Manifestly, each such operation, broadly viewed, may be considered, in an estimate of the situation, as a course of action. Each such course of action (or operation) will involve, if developed into a more or less complete plan of action, numerous detailed operations which constitute parts of the whole. (See [page 37].)
There can be no rigid line of demarcation, always applicable, between courses of action and the more detailed operations pertaining thereto. For example, "to raid" may be, in one instance, an operation of such a character, from the viewpoint of the commander, as to be envisaged, correlatively with "to destroy", as one of his courses of action. Yet, in another problem, a raid may be visualized, properly, as a detailed operation pertaining, in a subordinate capacity, to a more comprehensive operation envisaged as a course of action "to destroy".
Similarly, what is a broad course of action from the viewpoint of one echelon in the chain of command, may be correctly viewed, on a higher echelon, as a detailed operation. Operations assigned in tasks imposed by higher authority become the basis for the determination of courses of action on the next lower echelon, a procedure which continues throughout the chain of command until specialized, on the lowest echelons, in the form of a simplified routine (see [page 84]).
While the list of courses of action given above is made up from the viewpoint of broad strategical problems, a similar list can be assembled for other problems. For example, the order, "Destroy enemy naval forces", if taken as the motivating task of a tactical estimate, will be the basis for certain courses of action, constituting, when complete (see below), a well-recognized general plan for a naval battle. This plan will in turn call for various detailed operations on the part of the several subdivisions of the force under the commander who makes the estimate (see [page 95]).
As a tentative solution of the problem a course of action may be complete or partial, i.e., it may, if carried out, provide for the complete attainment of the objective; or, such complete attainment may require a combination of several of the courses of action under study.
The exclusive consideration of courses of action of the complete type possesses the advantage of minimizing the total number of solutions under study. This simplifies the procedure of analysis and of comparing courses of action with each other, because of the relatively small number of courses to be tested and to be compared.