Seacoast Defense (US)

Seacoast defense was a major concern for the United States from its independence until World War II. Before airplanes, America's enemies could only reach her from the sea, making coastal forts an economical alternative to standing armies or a large navy. After the 1940s, it was recognized that fixed fortifications were obsolete and ineffective against aircraft and missiles. However, in prior eras foreign fleets were a realistic threat, and substantial fortifications were built at key locations, especially protecting major harbors.

The defenses heavily depended on fortifications but also included submarine minefields, nets and booms, ships, and airplanes. Therefore, all of the armed forces participated in seacoast defense, but the US Army Corps of Engineers played the central role in constructing fixed defenses.

Designs evolved and became obsolete with changes in the technology available to both the attacking forces and the defenders. The evolution of the US seacoast defense system is generally identified among several "systems", which are somewhat defined by the styles used, but more so by the events or trends which periodically stimulated new funding and construction. The division of the early forts into the First and Second Systems was made by later historians, and appears officially in an 1851 report by Chief Engineer Joseph Totten, probably the most prolific builder of masonry forts in American history.

At the beginning of the American Revolution, many coastal fortifications already protected the Atlantic coast. Prior to independence from Britain, local communities or colonies bore the cost and responsibility for their own protection. Urgency would wax and wane based on the political climate in Europe. Most defenses were artillery protected by earthworks, as protection from pirate raids and foreign incursions. Though seldom used, the forts were a deterrent. Additional forts, called Patriot batteries, were built during the Revolution, usually to meet specific threats.

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