(4) Fourth step: The supervision of the planned action, in the fourth step, may involve a new strategical problem, perhaps several. In such event each new basic problem will initiate a new series of problems, with corresponding directives, as described above. Changes in strategical plans may be called for. If no strategical changes are involved, there may nevertheless be introduced one or more new tactical or logistics problems, with corresponding changes in the subsequent procedure. The fourth step may, however, merely involve changes in supporting plans (tactical, logistics, etc.), with resultant changes in the directives involved. Finally, the fourth step may involve changes, for clarification, in the directives formulated in the third step. Variations in the foregoing procedure are frequent. The most usual is perhaps the case where the commander, receiving a tactical (instead of a strategical) mission, solves such a tactical problem as a basic problem in the first step; resolves his Decision into detailed tactical operations in the second step; issues a tactical directive or directives in the third step; and supervises his planned tactical action in the fourth step. Phraseology as to "Course of Action", "Operation", and "Task". It is important to avoid the possibility of becoming confused because each of the terms "a course of action", "an operation", and "a task", is correctly visualized as "an act or a series of acts". In the first step, the selected course of action (see page 104) indicates the "act or series of acts" decided upon as representing, in general terms, an effort for attainment of a specified objective and is therefore stated as a comprehensive method of attaining that objective. The Decision thus adopts this course of action as a general plan of operations, or as a basis therefor. In the second step, the required action is developed to place it upon a practical, workable basis as a detailed plan to be executed. The "act or series of acts" represented by the selected "course of action" has now become a detailed "act or series of acts". As such, it is now susceptible of being assigned, in whole or in part, to subordinate commanders as "tasks". The cycle within that particular echelon is completed when the tasks are thus assigned. The commander has thereby charged his immediate subordinates with the commission of specific "acts or series of acts". Each such subordinate commander necessarily decides on the best method of accomplishing his assigned task, i.e., on the course of action (act or series of acts) which will best accomplish the effort required of him. The procedure (for each commander on that echelon) thus begins anew until an echelon is reached where the character of the required action has already been determined as a matter of routine (see page 84). The Use of a Form in the Solution of Problems