ABSTRACT
THE encampments of enemy forces are set up where there are natural defences much more often than on bare rocks and flat ground, so that it costs as much trouble to pit one's careful shrewdness and dexterity against Nature's fortifications as against the might of the foe. A similar level of cunning is needed when it is seen that long bridges over rivers have been unexpectedly broken down by the strong current or by an enemy.1
