For example, a first consideration might be "to reduce enemy carrier aircraft strength by" certain pertinent operations. A second consideration might be "to reduce enemy battle-line speed by" certain operations in order to force the enemy to accept battle. A third might be "to reduce enemy battle-line speed, life, and hitting power by gunfire" within certain range bands, in order to exploit own strength and enemy weakness at those ranges. A fourth might be "to continue reduction of enemy battle-line strength by gunfire, closing to" such a range as is suitable to that end. Finally, a fifth consideration might be "to inflict conclusive damage on enemy battle-line with torpedoes". All of the foregoing partial courses (other possibilities having been studied and discarded) might then be combined into one operation as the selected course of action "in order to destroy the enemy battleship strength",--such destruction being the assigned objective. The degree of detail in which a course of action may be visualized for purposes of the estimate will vary with the same factors, i.e., personal facility and the nature of the problem. Practice in the solution of problems appears to develop such facility that entire plans can be visualized as courses of action, each plan reasonably complete as to details with reference to physical objectives, relative positions, apportionment of fighting strength, and provision for freedom of action. However, it is rarely, if ever, necessary to visualize courses of action minutely in an estimate of a basic problem; the extent to which they are viewed mentally, as detailed plans, need only be such as to fulfill the requirements of the particular problem (see Section I of Chapter IV). The statement of a course of action, for purposes of the estimate, will naturally be along broad and comprehensive lines, although some important matters of detail (relatively speaking) may be added if this is found desirable as the estimate proceeds. It is with these considerations in mind that the standard practice has been developed of formulating courses of action, while under study as tentative solutions of the problem, in broad terms, appropriate to general plans of action. The commander may find, on occasion, what appears, on first examination, to be an exception to the rule, herein treated as valid, that a course of action, correctly conceived, always contains the two elements (1) objective, specific or inferred, and (2) action for its attainment. However, apparent exceptions to this principle are due to special conditions which, on proper analysis, reveal no actual exceptions. Certain examples, now to be discussed, demonstrate this fact. For instance, when the higher commander deems such procedure advisable (page 86), he may make his subordinate's estimate of the situation, as well as his own, and may accordingly indicate both a task and a predetermined course of action for the subordinate to pursue: for example: