b) Comparison of gains and costs. When costs are found to be
in excess of the over-all gains, this fact may be the basis
for rejecting any courses of action which are less desirable
than others. However, retention of a course found to be costly
may be justified for sound reasons.

* * * * *

When, as in the example given previously (page 96), the commander
receives a directive such as "Deny enemy base sites in the area ABCD
by capturing X Island", he carries through his estimate of the
situation in the usual manner. He notes, however, that the capture of
X Island has been indicated as a predetermined course of action. He
makes a proper survey of the factors of relative fighting strength. He
considers all pertinent courses of action. He goes through this
procedure in order to reach an understanding of all the elements of
his problem. He wishes to understand the necessary background. He
realizes the importance of a grasp of the considerations which have
led higher authority to arrive at the predetermined course of action.

By carrying through the usual estimate procedure, including the
analysis of all pertinent courses of action, he assists himself to
arrive at a proper concept of the action to be taken to capture X
island. In this way he establishes a sound basis for formulating a
detailed plan (in the second step), for inaugurating planned action
(in the third step), and for supervising this action (in the fourth
step). He also establishes a basis for any constructive
representations which he finds it advisable to make to higher
authority (page 15).

In another example previously given (page 96), the higher commander
indicates only the predetermined course of action (by a directive
"Capture X Island") and omits the statement of the true underlying
task. The subordinate, on discovering this fact, deduces the
underlying task and carries through the estimate procedure, modified,
as explained for the previous example. In addition to the merits as
previously stated, this method has a further advantage. The deduction
of the underlying task enables the commander to judge whether any
advisable or necessary deviation or departure from the predetermined
course of action (page 15) involves merely a variation from the letter
of his instructions or, more important, from their spirit.

For instance, the directive, as in the case previously discussed, may
have been "Capture X Island