the day.

To rely upon rules of action which do not express the whole truth is
to court the danger of encountering exceptions which may entail
serious consequences. The value of those rules known to be
inexpressive of the whole truth lies in the fact that they may invite
attention to circumstances which are sometimes encountered, or may
suggest methods of action which are sometimes appropriate. Danger lies
in the fact that such rules may fail to give proper emphasis to other
circumstances or other methods which are encountered or are more
appropriate in other cases.

Such a rule may fail to consider the entire problem. Its use,
therefore, implies the necessity of recognizing cases to which it is
not applicable. This may frequently be difficult in the active
operations of war, when nervous strain and the urgency of events are
handicaps to quick and accurate thinking (see page 22).

To express the whole truth, a rule of action calls to attention all
circumstances, or causes, which may ever influence the result. The
saying that "the exception proves the rule" is properly interpreted
only in the older sense that an exception "tests" the rule, indicating
by the mere fact of exception that the rule is to such extent
incomplete.

Subject to variations of phraseology, the old adage "circumstances
alter cases" is the sole reliable and fundamental rule of action. A
corresponding maxim of the military profession, "It depends on the
situation", has its root in recognition of the same fact, i.e., that
the action taken in any situation depends, properly, on the
circumstances of the case, and that the relationship between cause and
effect (page 22) is always the governing consideration. The principles
deduced hereafter (Chapter III) have these irrefutable findings as
their foundation.

Factors. A situation is by definition (page 20) a combination of
circumstances, which are the effects of certain causes. To these
causes, the term "factors", long in use in the military profession, is
customarily applied in many other activities. Through their influence
as causes, these factors operate to produce, as their effects, the
circumstances which, in combination, constitute the situation. A
combination of factors, therefore, gives to each situation its
distinctive character, differentiating it from other situations.

To maintain an existing situation, it is necessary to preserve, in
total effect, the influence of factors already presen