An example of this method would occur where several rather specific operations were visualized, involving seizure of certain localities as a defensive measure. If it were then observed that the objective in each such case was "denial to the enemy of a particular naval-base site in the area ABCD", an appropriate expression of a comprehensive course of action would be "to deny the enemy naval-base sites in the area ABCD". Another method of visualizing appropriate courses of action seems to involve initial recognition, in the first instance, of such courses as broad and comprehensive general plans, without first visualizing and combining their details. This method appears to be more usual after considerable experience or training. It is therefore possible that this second method is merely a practiced development of the first, the process of synthesis being so rapidly accomplished that it becomes subconscious. The nature of the particular problem has also an unquestioned bearing on this subject. In instances where no single course of action can be found which is adequately expressive of complete attainment of the objective, the final selection of a method of attaining the objective will necessarily be through a combination of the courses of action under study (page 93). For example, if the assigned task were to "protect trade in sea area ABCD", the extent of the area, together with its geographical position relative to locations from which enemy attacks could be launched, might not be such as to permit the attainment of the objective by a single course of action such as "to escort trade in convoys" or "to patrol the trade routes". Both of these courses of action might be necessary, and, in addition, perhaps, the further course "to cover focal points M and N". Each of these courses of action has, as its objective, the establishment of a protected area or areas, stationary or moving, for the safe passage of merchant vessels. However, for purposes of expressing the course of action involved, the contemplated procedure is in this case better indicated by a combination expressed in terms of action, the objective being inferred as a matter of mutual understanding. The less particularized expression of the course of action in terms of the objective would, in this instance, convey a less definite idea of the procedure under consideration. Similar considerations pertain frequently to naval problems, more especially to those involving naval engagements of considerable scope. The solution of such a problem takes, typically, the form of an operation consisting, not of a single "act", but of "a series of acts", i.e., of a number of stages or phases of battle, each being a preparation for the one following, until the final stage provides for the attainment of the assigned objective.