The application of the estimate procedure to the second step may be tested, aside from the logic of the theory involved, by careful analysis of examples. For instance, if the basic Decision was to determine the location of enemy forces in the area ABCD, this becomes the basis for a plan embodying the best method of determining the location of such enemy forces (an operation, or a series of operations). One method of procedure (course of action) to achieve this objective may be to search the area by aircraft; another may involve a search by cruisers; another by destroyers; another by submarines; etc. The operation or operations finally determined upon may be any one of these, or a combination of two or more of them, perhaps of all of them. The fundamental procedure leading to this conclusion is identical with that of the basic estimate. There are a number of possible variations of the fundamental mental processes applicable to the second step, according to the facility and the preference of the commander. Practice seems to develop such facility (see also page 94) that entire plans, each properly integrated with respect to physical objectives, relative positions, apportionment of fighting strength, and freedom of action, may be visualized separately from each other. At the other extreme, the elementary procedure is to utilize these salient features of such a plan, successively, to suggest detailed operations. The features after the first are then used either to adapt or to complete the operations suggested by preceding features, or to suggest new operations. This elementary procedure, being the simpler and more methodical of the two, is the one explained hereafter (Chapter VII). However, there are various possibilities as to procedures intermediate between these extremes. One such procedure would visualize operations primarily on the basis of correct physical objectives, adapting and completing such operations by reference to the other features; the procedure would then utilize relative positions, etc., to suggest additional operations, which in turn may be similarly adapted or completed. The commander is of course at liberty to use the procedure best suited to his own working methods and to the particular situation; naturally, he bears full responsibility for any errors due to a faulty choice of procedure. From the standpoint of the exercise of mental power in the solution of military problems, the second step may be taken to include the assembly of the commander's conclusions in the form of directives. The third step begins, however (page 107), when the commander forms the intent of immediately promulgating such directives.