It is also possible that, during the progress of an operation, an unforeseen opportunity may present itself to take advantage of a new situation and to strike the enemy a more serious blow than that originally intended. Unwise caution is to be avoided no less than undue temerity. Where a change appears, after proper consideration, to be indicated, no hesitancy is justified in abandoning the original plan. Blind adherence to plan is to be condemned no less than unwarranted departures from predetermined procedure. Obstinate insistence on the use of a certain method, to the exclusion of others calculated to attain the same effect, may jeopardize the success of the effort. Undue emphasis on the particular means to be used, and on the manner of their employment, may exact a penalty by obscuring the objective. On the other hand, undesirable departures from plan involve a corresponding penalty, because changes, unless duly justified by the situation, increase the possibility of failure. Frequency of such changes, to the point of vacillation, is a sure indication of a lack of aptitude for the exercise of command. Importance of the Will of the Commander. It is accordingly clear that qualification for the exercise of command requires the mental capacity to recognize the need for changes in plan, or for no change. No less essential, however, are the moral qualities required to carry justified changes into effect, or to resist the pressure of events in favor of changes not justified by the situation. (See also pages 8, 9, and 72.) Hence the universal importance accorded, by the profession of arms, to the will of the commander. This is the quality which, together with the mental ability to understand what is needed, enables the commander to bend events in conformity with his plan (page 47), or, where such shaping of circumstances is infeasible, to ensure for his command every possible advantage which can be obtained. A recognized defect of certain forms of theoretical problems lies in the fact that they indicate, themselves, the time when a Decision is needed. In other words, they fail to vest the commander with responsibility for the decision that the time has come for a Decision to be made. Hence the great importance, from the viewpoint of timing, of those problems and exercises which partake more fully of the reality of war. The successful conduct of war, notwithstanding its demand for utmost mental power, is founded predominantly on those moral qualities (see pages 9 and 72) which spring less from the intellect than from the will. Problems Involving Modifications of the Basic Plan Relatively minor deviations from decisions reached during the first and second steps of the solution of a military problem are frequently required during the action phase, because of incentives arising from the demands of the situation. Such requirements will not occasion serious dislocation in the predetermined effort of the competent commander.