When completed in 1847 with its 25 million bricks and walls 7.5 feet thick, Fort Pulaski was the ultimate defense system of its day. Part of a series of forts which protected major seaports from foreign attack, the stronghold would not be tested until the Civil War. Seized by Georgia state troops early in the war, the fort was besieged by Federal forces. Here on April 11, 1862, defense strategy changed worldwide when Union rifled cannon, firing from more than a mile away on Tybee Island, first over came a masonry fortification.