In battle, there are not more than two methods of attack–the direct and the indirect; yet these two in combination give rise to an endless series of maneuvers.
Hence that general is skilful in attack whose opponent does not know what to defend; and he is skilful in defense whose opponent does not know what to attack.
There are roads which must not be followed, armies which must not be attacked, towns which must not be besieged, positions which must not be contested, commands of the sovereign which must not be obeyed.
