Troops taken being of equal strength, he who captures the rear of one who has gone against a wandering enemy gains more advantages; for one who has marched out against a wandering enemy has to put down the rear-enemy only after obtaining an easy victory over the wandering enemy; but not one who has marched out against an entrenched enemy, for one who has marched out against an entrenched enemy will be repelled in his attack against the enemy's forts and will, after his return, find himself between the rear-enemy, and the frontal enemy who is possessed of strong forts.