'A besieged fortress can be compared to a man suffering from gangrene. In the same way that he must sooner or later succumb, so, too, must a fortress fall. The doctor and the commandant should realize this fact from the very first day that the former is summoned to the bedside of the patient, and the latter placed in command of the fortress. This, however, does not prevent the former believing in miracles, or the latter hoping for a happy issue by external relief. And this belief is more necessary for the latter than the former, provided it is not so great as to make him careless. Gangrene attacks a man in his extremities--_i.e._, in the toes--and it is the doctor's duty to separate the part affected. His task consists in prolonging the patient's life, and the commandant's in postponing the date of the fortress's fall. The doctor must not allow the patient suddenly to die, any more than the commandant must allow the fortress to fall suddenly through some unforeseen circumstance. The patient should succumb gradually, beginning with the extremities, and so should the fall of the fortress be gradual, beginning with its outworks. Successes with the first, as with the second, will depend upon the extent to which the infected member is in time removed, or the attacked position is abandoned. This task is no easy one; the doctor must be a skilled professional to be able to fix the moment when the diseased organ is more harmful than useful; but this alone is insufficient, for the patient must first be persuaded to agree to amputation, as without his consent the operation will be impossible. Who cares to lose a leg or an eye? Some would prefer to die, and the doctor must be able to persuade the invalid that it is possible to get about without a leg, that an American artificial leg will enable him to dance. Nor is it easy for the commandant, who must have a thorough grasp of the situation, to be able to know when an attacked position has inflicted all the loss that it can inflict on the attacker, and to recognize the moment when the balance of superiority passes to the enemy. The skill _consists in being able to abandon a position before the final blow is delivered_, and at the same time to sell the enemy his success dearly. It must be borne in mind that fortress warfare resembles rear-guard fighting, a fact which does not seem to be appreciated by everyone. But besides eyes the commandant must have character, for commonsense and conscience will call out "Retire!" while sentiment and anger will cry "Hold on!" He does not know what he can get--like the artificial leg--in place of what he loses. With the doctor it is different, because his medical store contains false limbs, the commandant's does not. The doctor amputates the infected organs so as not unnecessarily to waste the life's blood, keeping it for the heart. The commandant abandons