Fort Pulaski was considered invincible with its 7-1/2-foot solid brick walls and reinforcing masonry piers. General Robert E. Lee had earlier surveyed the fort's defenses with Colonel Olmstead and determined, "they will make it pretty warm for you here with shells, but they cannot breach your walls at that distance." Wide swampy marshes surrounded the fort on all sides and were infested with native alligators. No attacking ship could safely come within effective range, and land batteries could not be placed closer than Tybee Island, one to two miles away. Beyond 700 yards, smoothbore guns and mortars had little chance to break through heavy masonry walls. Beyond 1,000 yards, they had no chance at all. The U.S. Chief of Engineers, General Joseph Gilbert Totten, is quoted as saying, "you might as well bombard the Rocky Mountains." If there were ever to be a successful siege, it would have to starve the garrison into submission.