170. A striking example of the fatal consequences that may issue from an undue accumulation of artillery in small earthworks is to be found in the attempted defense of Port Royal Harbor by the enemy in November, 1861. All his artillery on that occasion was collected in two small forts, one on each side of the harbor. Into these our fleet in its circuits within the harbor poured successively an overwhelming and concentric fire, and drove the enemy from them by sheer weight of metal, before the works themselves had sustained any material injury. There were no bomb-proof shelters for the men in either work. Had the enemy's artillery been distributed along the opposite shores for a distance of 400 or 500 yards, in batteries of one or two pieces each, the result viewing the action as one between land and naval batteries simply, might have been quite different.
As security against attack in rear by troops, the infantry supports should have been placed in inclosed works in rear of the batteries.
171. The special defense of Fort Wagner was faulty in two particulars, viz:
First. It was too passive. All the advantage that might have been derived from vigorous night sorties, against which the fire of the fleet could have taken no part, was voluntarily relinquished when the system of defense by torpedo mines placed on and in advance of the glacis was resorted to.
Second. Curved fire was not used enough. The armament of the work contained but two mortars (one 8-inch and one 10-inch). These, when earnestly served, caused the most serious delay in the progress of our works, and on one occasion suspended it entirely.
172. The Coehorn mortar is a most valuable weapon in siege operations. From its lightness and portability it is peculiarly adapted to the attack, and should follow close on the heels of the sappers. This leads to in inquiry into the military principles which controlled the issued of the contest for the possession of Morris Island, under the peculiar circumstances of the case, after we made our lodgment there on the 10th of July, viz: Our forces occupying one end of the island without batteries or defenses of any kind excepting what were improvised from day to day, the enemy being upon the other end strongly fortified (the narrowest part of the island, a mere strip of shallow sand frequently overflowed the sea, being between the contending forces, and within half musket range of the enemy's batteries), and both parties having their communications to the rear open, why did not the enemy drive us from the island, as their commander asserted should be done, instead of being driven from it themselves?
Two conditions, steadily maintained, achieved success for us, viz:
First. An overpowering mortar fire from our batteries, particularly toward the end of the siege of Fort Wagner, opposed by a weak one from the enemy.
Second. The difference, always in our favor, excepting in rough weather, between the flank fire upon us from the James Island batteries, and the fire upon the enemy from our fleet, which could establish comparatively short ranges, and had considerable latitude in selecting positions. These considerations induced the enemy to adopt and injudicious, because passive, defense. They depended mainly on torpedo mines for the security of their position. These would have been useful against open assaults, but should have been removed to facilitate night sorties, as soon as we resorted to the attack by regular approaches.