The Battle of Port Royal Sound demonstrated to Lee that without adequate naval support it would be impossible to defend the small batteries and forts on the seacoast islands which were all within range of the powerful guns of the Federal fleet. Nor would it be possible to prevent enemy landings on these beach islands without immobilizing thousands of troops for garrison duty, troops that were badly needed in other theaters of war. Even if the manpower could have been spared for island defense, the logistical difficulties of arming and supplying isolated and remote outposts were beyond the capacities of the State or Confederate Governments. With these considerations in mind, Lee ordered the abandonment of the sea islands of Georgia, the removal of the guns from the batteries, and the withdrawal of the troops to the inner line of defenses on the mainland. This strategy was later confirmed and made the policy of the Confederate Department of War. On November 10, Tybee Island was abandoned. All batteries were leveled and the heavy guns were ferried across the South Channel to Fort Pulaski. Two companies of infantry from the Tybee garrison were added to the complement at the fort and the remaining troops were withdrawn to Savannah. This was a fateful move for it directly affected the destiny of Fort Pulaski. At the time, however, no new danger to the fortification on Cockspur Island was anticipated through the abandonment of Tybee Island. It was expected that the fort could defend itself successfully against a naval attack and it was also considered safe from land bombardment. To keep open a line of communications and supply, all side channels leading into the Savannah River above the fort were barred by obstructions. These obstructions, in turn, were protected by floating mines activated by galvanic batteries. The mines, or “infernal machines” as they were called in the naval report, were a new invention which the Confederates borrowed from the Russians. The responsibility for denying the Federal gunboats an opportunity to force a passage through the obstructed side channels into the Savannah River was assigned to Tattnall’s flotilla. In theory, at least, it should have been possible to hold out at Fort Pulaski indefinitely. When the supply line was finally cut, it was not due to any failure in the plan for the protection of the river, but rather to a lack of vigilance on the part of the Georgia Navy, which permitted the Federals to construct strong batteries in the marshes on the north and south banks of the Savannah between the fort and the city. Twice during November, General Lee inspected the fort on Cockspur Island and gave minute instructions regarding the manner in which it was to be defended. He foresaw the danger of attack from the rear and ordered certain guns to be mounted on the ramparts above the gorge.