The fall of Fort Pulaski signaled the obsolescence of masonry forts in the face of the newest rifled artillery technology.  Left alone and isolated, no brick and mortar land fort would be able to survive a sustained bombardment.
          In response, and out of necessity, the Confederacy moved toward earthen forts to protect their harbors and waterways.  Famous examples include Fort Fisher guarding Wilmington, North Carolina, and Fort McAllister guarding the Ogeechee River south of Savannah.  Earth walls allowed the force of the rifled projectiles to be absorbed, and the walls could be easily rebuilt.  Such forts would have to be taken by land-based infantry.