Seacoast Defense in The United States - Civil War

Civil War

Again changes in technology affected design; the higher velocity ordnance of new rifled cannons crushed and penetrated the masonry walls of Third System forts. Severe damage was inflicted to forts on the Atlantic Coast during the Civil War. For example, Fort Sumter in South Carolina was bombarded into surrender by Confederate batteries in 1861, and reduced to rubble during Union efforts towards its recapture. In 1862 Fort Pulaski in Georgia was forced to surrender after only 30 hours of bombardment with rifled cannon.

During the Civil War, naval officers learned that their steamships and ironclad vessels could run past southern Third System forts with acceptable losses.

The urgencies of war required that new forts or improvements be constructed quickly and at low cost. Partially completed Third System forts were finished, but new construction was mostly wood-revetted earthworks. Frequently earthworks were built near a Third System fort in order to supplement its firepower, but often they were stand-alone fortifications. In some cases cannon from masonry forts were dispersed to earthen bunkers where they were better protected. The fortification of San Francisco Bay is a good example, where the typical Third System Fort Point at the mouth of the bay was effectively replaced by dispersed earthworks and low-walled fortifications nearby on Alcatraz Island, Angel Island, the Marin Headlands, and Fort Mason.