Subsidiary problems, according to their nature in each case, may be solved by the procedure distinctive of the first step or by that distinctive of the second. In many instances either may be applicable, the choice being a matter of convenience.
Battle Plans, for example, can demonstrably be formulated by the use of either procedure. Thus, a Decision "to destroy the enemy in a daylight fleet engagement" may be used as the basis for an Estimate of the Situation, by the procedure distinctive of the first step, in order to reach a decision as to the plan, in outline, for the contemplated engagement. However, the same result can also be attained through the procedure distinctive of the second step, with the basic Decision as the point of departure.
A solution also can be reached by a method which is, in effect, intermediate between the procedures of the first and second steps. For example, the basic (broad strategical) Decision noted above can be taken, in a detailed tactical Estimate, as the only suitable, feasible, and acceptable course of action. Then, in Section IV of the Estimate, a study of the more detailed operations involved can be developed into an outlined plan for the battle. Thus, a single course of action, expanded to include the outlined plan so developed, can then be adopted as the decision and can in turn be expanded by second-step methods into a detailed tactical plan.
On the grounds of simplicity, the procedure distinctive of the second step is preferable, when it is applicable to the particular problem. Therefore, when a subsidiary plan is to be developed directly from a basic Decision, this is frequently the better procedure. This comment is applicable not only to battle plans but also to other subsidiary plans such as sortie plans, entrance plans, and logistics plans. The commander may find it necessary, however, to expand the study of fighting strength made in Section I-B of the basic estimate, in order to obtain the detailed data needed for formulating the subsidiary plan.
In spite of the relative simplicity of the second-step method, cases occur where the procedure of the first step is nevertheless preferable. For example, a basic Decision making provision for a major campaign, divided into stages of some scope, may involve, as part of one of these stages, an operation to capture an island. Such an operation may itself require a considerable effort on the part of the whole force; yet the operation may be so specialized or localized, or both, with reference to the entire effort contemplated in the basic Decision, that the solution of this subsidiary problem can best be accomplished through the procedure distinctive of the first step.
The commander will therefore necessarily be the judge, in each case, as to the particular procedure to be adopted.
There are wide variations in the requirements of the Estimate Form, when used for the solution of subsidiary problems. This is natural because these problems vary widely in nature. They include, on the one hand, problems dealing directly with the conflict of armed forces, for which the Form is especially designed. On the other hand, these problems include those dealing with the factors related to freedom of action. To be suitable for this purpose, the Form requires modification in varying degrees. Certain examples are included in the latter part of this chapter ([page 176] and following).
The application of the procedure of the first step to the solution of such subsidiary problems requires provision for deriving, in each case, a (subsidiary) mission appropriate to the problem. Of the two elements of the mission, the (subsidiary) purpose is first determined, because the (subsidiary) task will necessarily be suitable to the (subsidiary) purpose. These elements of the (subsidiary) mission may be obtained from one or more of the operations into which the basic Decision has been resolved. They may also be obtained from a preceding subsidiary problem, already solved.
In illustration of the preceding, discussion is first centered on a strategical problem of usual type, involving a subsidiary tactical problem calling for the detailed employment of weapons in a naval engagement. Other illustrations will deal with subsidiary problems relating to particular aspects of freedom of action.
In the first example it is supposed that the commander has already solved a basic problem of broad strategical scope, and has arrived at a Decision which contemplates an engagement. A further logical act of planning is now to develop a Battle Plan. Such development involves the solution of a subsidiary problem. In this case the commander is supposed to have found it desirable to solve this subsidiary problem by the procedure distinctive of the first step.