less valuable than a principle. The former may be originally faulty,
or may cease to apply through change of circumstances; the latter has
its root in the essential nature of things, and, however various its
application as conditions change, remains a standard to which action
must conform to attain success. War has such principles; their
existence is detected by the study of the past, which reveals them in
successes and in failures, the same from age to age. Conditions and
weapons change; but to cope with the one or successfully wield the
others, respect must be had to these constant teachings of history in
the tactics of the battlefield, or in those wider operations of war
which are comprised under the name of strategy.

It is however in these wider operations, which embrace a whole theatre
of war, and in a maritime contest may cover a large portion of the
globe, that the teachings of history have a more evident and permanent
value, because the conditions remain more permanent. The theatre of
war may be larger or smaller, its difficulties more or less
pronounced, the contending armies more or less great, the necessary
movements more or less easy, but these are simply differences of
scale, of degree, not of kind. As a wilderness gives place to
civilization, as means of communication multiply, as roads are opened,
rivers bridged, food-resources increased, the operations of war become
easier, more rapid, more extensive; but the principles to which they
must be conformed remain the same. When the march on foot was replaced
by carrying troops in coaches, when the latter in turn gave place to
railroads, the scale of distances was increased, or, if you will, the
scale of time diminished; but the principles which dictated the point
at which the army should be concentrated, the direction in which it
should move, the part of the enemy's position which it should assail,
the protection of communications, were not altered. So, on the sea,