Situations may be encountered when, in the equation referred to in Section II-B (page 135), no value can be assigned the factor of the appropriate effect desired which will constitute a sufficient basis for deducing enemy courses of action. Such situations are not unusual, especially in problems of lesser scope. In such cases, the commander is compelled to consider all possible enemy courses of action which can materially influence his own plan. Therefore, in instances of this nature, it is apparent that the procedure of giving first consideration to the commander's own courses of action affords the advantage of (see page 134) narrowing the field as to the enemy capabilities. B. Survey of Enemy Capabilities. If, then (to repeat, because of the importance of the matter), the commander believes that he has, in the deduced enemy effect desired, a sufficient basis for evolving all pertinent enemy capabilities, he now proceeds, by the mental process described in Section II, to list the enemy courses of action which he thinks merit attention. If there be no adequate basis, the commander will find it desirable to list all enemy courses of action which can materially affect his own effort. The survey of fighting strength (Section I-B) has established, through consideration of the "means available and opposed", and of the "characteristics of the theater", the limitations of enemy capabilities from the standpoint of feasibility. Because, however, so much of the enemy's situation is usually conjectural, it is important to give the most searching attention to the comparison summary in Section I-B,--in fact, to consider fully every element of weakness and strength, and of advantage and disadvantage. Such a study will disclose every possibility which the enemy might exploit. The commander may thus determine, for example, the enemy strength which can be moved into positions within time limits that can affect the commander's courses of action; he can also examine into possibilities of obtaining information concerning the enemy's moves. Such a study enables the commander to envisage the enemy operations which presumably can materially affect his own plans. He may now list the presumed capabilities of the enemy, in the form of courses of action, for purposes of further analysis. Naturally, he lists courses which appear to be suitable, feasible, and acceptable as to consequences, but formal tests are deferred until the next phase of the estimate. C. Application of Tests for Suitability, Feasibility, and Acceptability. Having listed pertinent enemy courses of action as described above, the commander next tests them for suitability, for feasibility, and for acceptability as to their consequences.