Seacoast defense in the United States Seacoast defense was a major concern for the United States from its independence until World War II . Before airplane s , 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 fortification s 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 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 . 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 . Early defenses . 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 were built during the Revolution ; usually built to meet specific threats . First system . When the United States gained independence in 1783 , the seacoast defense fortifications were in poor condition . Concerned by the outbreak of war in Europe in 1793 , the Congress created a combined unit of artillerymen and engineers in 1794 , appointed a committee to study coast defense needs , and appropriated money to construct a number of fortifications that would become known as the First System . Twenty - one locations were selected to be fortified , mostly with traditional low walled structures with low sloped earthworks protecting wood or brick walls . The conventional wisdom was that soft earth would cushion the effect of cannon fire against the walls , and that low walls presented less exposure to projectiles . Walls were laid out at angles to each other forming a system of bastions , resembling a star layout , so that enemy forces could not mass against the bottom of a wall beneath the vertical field of fire from the wall ; defenders on any wall could see and fire - on the base of the adjacent walls . The angled walls also reduced the chance for more destructive straight - on hits from cannonballs . Lacking trained engineers to supervise the work , Secretary of War Henry Knox placed a number of European engineers under contract . Although some fine forts were constructed , for the most part enthusiasm and funding waned and little work was completed . Most of the partially finished earthworks and wooden structures deteriorated before they were needed to defend against the British in 1812 . Second system . In 1802 Congress separated the artillerists and engineers into separate corps and directed the Corps of Engineers to create a military academy at West Point , New York . One of the driving forces for establishing the new academy was the need to divorce the United States from its reliance on foreign engineers . In 1807 - 1808 new concerns over a possible war with Great Britain , prompted President Thomas Jefferson to renew fortification programs ; this has come to be known as the Second System . One common weakness among the typical low - walled open bastion or star fort s was exposure to enemy fire , especially to new devices designed to explode in mid air and rain shrapnel down on the gunners . Gun emplacements which were at an angle to the sea were vulnerable to a solid shot running parallel to the wall taking out a row of guns and gunners with one enfilading shot . In the late 1770s a French engineer , the Marquis de Montalembert , advocated a major change in the design of fortresses to address these problems . His design protected a fort ' s gunners by placing most of them in covered casemate walls with openings for the guns . By stacking rows of casemates in high walls more guns could be mounted along shorter walls . This was particularly important for seacoast fortifications , which had only a limited time in which to fire at passing enemy ships . To build these tall forts , walls had to be built of masonry , but be very thick in order to withstand the pounding of cannon fire . The Second System was distinguished from the First System by greater use of Montalembert ' s concepts and the replacement of foreign engineers by American ones , many of them recent graduates of the new United States Military Academy superintended by Jonathan Williams ( engineer ) who not only instructed the new engineers in new thoughts of coastal defense , but also designed and constructed a prototype , Castle Williams in New York Harbor . Again several fine forts were produced , but generally projects went unfinished , and between the First System and Second System little was prepared to resist the British in the coming War of 1812 . However , no First System or Second System fortress was captured by the British . The invasion of Baltimore was prevented by Fort McHenry ( along with its protecting shoreline batteries of Forts Babcock and Covington to the west , Fort Look - Out ( or the Six - Gun Battery ) on the peninsula to the rear in the west , a temporary naval battery across the Patapsco channel to the east at Lazaretto Point , and the sunken ships blocking both channels on either side of McHenry along with 20 , 000 militia dug in on the east side of the town at " Loudenschlager ' s Hill " - later " Hampstead Hill " in today ' s Patterson Park ) . But undefended and unfortified , Washington the national capital ( with the exception of Fort Washington on the Potomac River just below Alexandria , Virginia was forced to surrender by the passing British fleet afterwards ) was burned after the land militia forces were routed at the Battle of Bladensburg northeast of the capital in Prince George ' s County . In some cases even incomplete forts ( some with fake wooden cannon barrels painted black pointed out the embrasures ) were sufficient to deter attack from the sea . Third system . In 1816 , following the War of 1812 , Congress appropriated over $ 800 , 000 for an ambitious seacoast defensive system which was known as the Third System . A Board of Engineers for Fortifications , appointed by President James Madison , visited potential sites and prepared plans for the new forts . The Board ' s original 1821 report established the policy which would remain in place for most of the 19th century . The original report suggested 50 sites , but by 1850 the board had identified nearly 200 sites for fortification ; however , forts were only actually built at 42 of these sites , with several additional sites containing towers or batteries . The main defensive works were often large structures , based on a combining of the Montalembert concept , with many guns concentrated in tall thick masonry walls , and the Vauban concept , with layers of low , protected - masonry walls . Construction was generally overseen by officers of the army ' s Corps of Engineers . Smaller works guarded less significant harbors . 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 . Minefields . During the Civil War underwater mines , at the time called a torpedo , became an important supplementary defense measure . The Confederacy , without a large navy to protect its harbors , relied on mines extensively to deter attacks by Union ships . Post Civil War . After the war , construction for several new Third System forts began in New England . These were to be built of stone rather than brick , and designed to accommodate the large - bore cannon developed during the war . However , in 1867 money for masonry fortifications was cut off , and the Third System came to a close . The vulnerability of masonry to rifled cannon and large - caliber smoothbore cannon and fewer concerns for invasion led to the construction of well - dispersed masonry - revetted earthen fortifications . During the 1870s , a number of new projects were started to include large caliber mortars and submarine mines . Cannon emplacements with brick - lined magazines were constructed and armed in some locations , but facilities for the mortars and mines were never completed . By the 1880s most of the earthen fortifications were in disrepair . Monitors for Coast Defense . Though coastal defense was generally within the purview of the army , the navy became more involved in the late 19th century with coastal defense ships , generally called monitors . These monitors were turreted ironclad warships inspired by USS " Monitor " ; as well as coastal ships which closely followed her design , the term ' monitor ' also encompassed more flexible breastwork monitors which had a modest armored superstructure and were thus more seaworthy . Monitor - style ships were used extensively in offensive roles during the Civil War , but were impractical for ocean service and offensive action abroad . They were , however , ideally suited for harbor defense with their shallow draft and large guns . Postwar , Civil War - era monitors were dispersed to important harbors , including San Francisco on the west coast . From the 1860s to the 1890s larger and more powerful monitors were produced , while the ocean - going navy was slow to make the transition to steel hulls and armor plating . By 1900 the navy was committed to ocean - going battleships , and they ceased producing monitors ; however , some of the vessels remained in service up to World War I in combat - prepared roles , and as training or auxiliary vessels thereafter . Endicott period . In 1885 US President Grover Cleveland appointed a joint army , navy and civilian board , headed by Secretary of War William Crowninshield Endicott , known as the Board of Fortifications . The findings of the board illustrated a grim picture of existing defenses in its 1886 report and recommended a massive $ 127 million construction program of breech - loading cannons , mortars , floating batteries , and submarine mines for some 29 locations on the US coastline . Prior efforts at harbor defense construction had ceased in the 1870s . Since that time the design and construction of heavy ordnance advanced rapidly , including the development of superior breech - loading and longer - ranged cannon , making the US harbor defenses obsolete . In 1883 , the navy had begun a new construction program with an emphasis on offensive rather than defensive warships . These factors combined to create a need for improved coastal defense systems . The Endicott Board ' s recommendations would lead to a large scale modernization program of harbor and coastal defenses in the United States , especially the construction of modern reinforced concrete fortifications and the installation of large caliber breech - loading artillery and mortar batteries . Typically , Endicott period projects were not fortresses , but a system of well - dispersed emplacements with few but large guns in each location . The structures were usually open - topped concrete walls protected by sloped earthworks . Many of these featured disappearing guns , which sat protected behind the walls , but could be raised to fire . Mine fields were a critical component of the defense , and smaller guns were also employed to protect the mine fields from minesweeping vessels . Coast Artillery Corps . 1901 reorganization . Robert Fulton used the term " torpedo " to describe the underwater explosive device in 1805 . Samuel Colt experimented with electrical firing of the torpedo . Electrical fired torpedoes , later termed mines , fired from mine casemates ashore were associated with coastal fortifications . As early as 1882 the need for heavy fixed artillery for seacoast defense was noted in Chester A . Arthur ' s Second Annual Message to Congress where he noted : Army leaders realized that heavy fixed artillery required different training programs and tactics than mobile field artillery . The Artillery Corps was divided into two types : field artillery and coast artillery . This process began in February 1901 with the authorization of 30 numbered companies of field artillery ( commonly called batteries ) and 126 numbered companies of coast artillery . 82 existing heavy batteries were designated coast artillery companies , and 44 new CA companies were created by splitting existing units and filling their ranks with recruits . The head of the Artillery Corps became the Chief of Artillery in the rank of brigadier general with jurisdiction over both types of artillery . The coast artillery became responsible for the installation and operation of the controlled mine fields that were planted to be under observation , fired electrically and protected by fixed guns . With that responsibility the corps began to acquire the vessels required to plant and maintain the mine fields and cables connecting the mines to the mine casemate ashore organized as a " Submarine Mine Battery " within the installation command . The larger vessels , Mine Planters , were civilian crewed until the creation of the U . S . Army Mine Planter Service ( AMPS ) and Warrant Officer Corps to provide officers and engineers for the ships designated as Mine Planters . The mine component was considered to be among the principle armament of coastal defense works . By the end of the Second World War such fixed coastal defenses were obsolete and the artillery branches were merged in 1950 with some of the Mine Planter vessels being transferred to navy and designated Auxiliary Minelayer ( ACM / MMA ) . Taft Board and creation of the CAC . In 1905 , after the experiences of the Spanish - American War , President Theodore Roosevelt appointed a new board , under Secretary of War William Howard Taft . They updated some standards and reviewed the progress on the Endicott Board ' s program . Most of the changes recommended by this board were technical ; such as adding more searchlights , electrification ( lighting , communications , and projectile handling ) , and more sophisticated optical aiming techniques . The board also recommended fortifications in territories acquired from Spain : Cuba and the Philippines , as well as Hawaii , and a few other sites . Defenses in Panama were authorized by the Spooner Act of 1902 . The Taft Program fortifications differed slightly in battery construction and had fewer numbers of guns at a given location than those of the Endicott Program . By the beginning of World War I , the United States had a coastal defense system that was equal to any other nation . The rapidity of technological advances and changing techniques increasingly separated coastal defenses ( heavy ) from field artillery ( light ) . Officers were rarely qualified to command both , requiring specialization . As a result , in 1907 , Congress split Field Artillery and Coast Artillery into separate branches , creating a separate Coast Artillery Corps ( CAC ) , and authorized an increase in the Coast Artillery Corps to 170 numbered companies . In 1907 the Artillery School at Fort Monroe became the Coast Artillery School , which operated until 1946 , and in 1908 , the Chief of Artillery became the Chief of Coast Artillery . Fort Drum . One of the most extreme fortresses of the early 20th century was Fort Drum in the Manila harbor of the Philippines . Originally a barren rock island , it was leveled by U . S . Army engineers between 1910 and 1914 and then built up with thick layers of steel - reinforced concrete into a massive structure roughly resembling a concrete battleship . The fort was topped with a pair of armored steel gun turrets , each mounting two 14 - inch guns . Searchlights , anti - aircraft batteries , and a fire direction tower were also mounted on its upper surface . The fortress walls protected extensive ammunition magazines , machine spaces , and living quarters for the 200 man garrison . The extensive fortification was not typical of the period , but driven by the exposed location . Although the design predated concerns about defense from air attack , the design proved to be exemplary for that purpose . After the outbreak of war in the Pacific on December 7 , 1941 , Fort Drum withstood heavy Japan ese air and land bombardment as it supported U . S . and Filipino defenders on Bataan and Corregidor , until the very end . The fortress was among the last US posts to hold out against the Japanese and did not surrender until ordered by superiors after the other major defenses had been overrun , but not until the US soldiers had sabotaged the guns and ordnance to prevent use by the Japanese . Ironically , even without the guns , the Japanese in Fort Drum were among the last holdouts when the US forces recaptured the Philippines in 1945 . Self - propelled torpedoes . Mines as we know them today were frequently referred to as torpedo es in the 19th century . The self - propelled torpedo as we know it was derived from the concept of the mine , with early submarine s and torpedo boats evolving as defensive weapons to deliver torpedoes against attacking fleets . During early development , it was not clear whether submarines and torpedo boats would be in the purview of the army or the navy , since the army was responsible for the use and development of stationary mine - fields . As the range and potential uses of submarines grew , it became more apparent that these were naval vessels , but both surface and submarine - delivered torpedoes were an important aspect of coastal defense strategies . World War I . Submarines and airplanes became more important , with the former being a perceived if not actual threat to US harbors . This concern caused an increase in the use of mines and nets , and demand for superior artillery . However , as the war progressed it became more clear that the enemies did not have the resources to bring the war across the Atlantic , and progress diminished along with concerns . Between the wars . Airplanes were a minor factor in World War I , but the threat prompted changes to coastal defenses in the 1920s and 1930s . Demonstrations in the 1920s by US general Billy Mitchell showed the vulnerability of warships to air attack ; this illustrated the use of aircraft for seacoast defense against ships , but also the vulnerability of defenses against air power . In the isolationist US , bomber s were seen as more of a defense against naval attack than a strategic offensive weapon . However , planes like the Boeing B - 17 , which evolved as defensive weapons , turned out to have excellent offensive capacity as well . In 1922 , 274 Coast Artillery companies were authorized and 188 were active . During the year 44 more companies were inactivated , but 14 new companies were created for the Philippine Scouts , and a 15th in 1923 . The general staff reconfirmed a commitment to artillery and mines as the most practical and cost - effective methods for seacoast defense , as an alternative to a larger navy or air corps . In 1924 the CAC returned to a regimental system , consolidating the companies into 16 harbor defense regiments and two of Philippine Scouts . The total companies authorized were 289 , with 144 active . From 1930 to 1932 the army drafted new defense projects for each harbor . In 1931 it established a Harbor Defense Board to supervise the execution of these projects . Existing batteries were camouflage d , but if detected , they remained vulnerable to air attack . Therefore , the next , and last , generation of coastal artillery was mounted under thick concrete shields covered with vegetation to make them virtually invisible from above . In anticipation of a conflict with Japan , most of the limited funds available between 1933 and 1938 were spent on the Pacific coast . In 1939 the threat of war in Europe prompted larger appropriations and the resumption of work along the Atlantic coast . The end of naval armament limitations during the 1930s allowed for larger and longer - range weapons on ships , which reemphasized the need for better long - range shore batteries . Large guns firing shells with ranges up to , which rivaled the latest naval weapons , were authorized , but there were few of them . Construction for the first 16 - inch emplacement began in 1936 at Battery Davis in Ft . Funston , south of the Golden Gate Bridge in San Francisco , California . The first test firing took place in 1940 , from Battery Townsley in Fort Cronkhite , north of the Golden Gate Bridge . In anticipation of war , additional mines , searchlights , radar , and anti - aircraft guns were installed in 1940 and 1941 . After the war began , the entire Western Defense Command was placed on high alert , but Japanese attacks , including two submarine attacks and an explosive balloon , caused only minor damage . Submarine nets and underwater mines protected many harbor entrances . Radar and patrol planes could detect enemy vessels at long distances , and aircraft became the first line of defense against intruders . World War II . The air attack on Pearl Harbor demonstrated the obsolescence of coastal artillery ; however , perhaps in its absence surface raiders would have been bolder . Coastal defense emplacements in the Philippines and Singapore were locally effective ; however , the Japanese just attacked where there were no defenses and then enveloped the fortifications . Heavily fortified positions such as Japanese Rabaul and Fort Drum in the Philippines demonstrated tactical success amongst a strategic failure . The United States planned an extensive Harbor Defense Armament Program during World War II to use stockpiled 16 - inch ( 40 cm ) naval rifles intended for the canceled battleships numbered 49 - 54 and battle cruisers numbered 1 - 6 and 8 - inch ( 20 cm ) naval rifles removed from USS New Jersey ( BB - 16 ) , USS Kansas ( BB - 21 ) , USS Minnesota ( BB - 22 ) , and USS New Hampshire ( BB - 25 ) . Plans were formulated for 38 new 16 - inch ( 40 cm ) batteries with a range of 25 miles ( 41 km ) , three new 12 - inch ( 30 cm ) army mortar batteries with a range of 17 miles ( 27 km ) , eleven new 8 - inch ( 20 cm ) batteries with a range of 20 miles ( 32 km ) , and 87 new 6 - inch ( 15 cm ) batteries with a range of 15 miles ( 24 km ) . Fortifications were planned for : Approximately a third of these batteries remained incomplete at the end of the war as a result of changing priorities ; and some on Oahu were completed with turrets from USS Arizona ( BB - 39 ) , USS Lexington ( CV - 2 ) and USS Saratoga ( CV - 3 ) rather than the designed guns . As tactics and strategies evolved throughout the war to become more reliant on sea - based air power in the Pacific and land - based battles in Europe , defending a harbor against ships became a superfluous activity , and even before the war ended , some seacoast guns were scrapped to become new weapons , and soldiers of the heavy artillery were transferred to anti - aircraft or even infantry duties . By 1947 most guns remaining in the seacoast defense were declared surplus , and the last weapons were removed in 1950 when the Coast Artillery was deactivated . Post war defensive missiles . Early in the Cold War , the Soviet Union developed long - range bombers which could reach the United States , and soon after exploded their first atomic bomb . Among the most threatened targets were harbors and naval bases . The mission of the Nike missile program was to act as a " last - ditch " line of air defense for selected areas . The Nike system would have been used if the air force interceptors failed . These were the last fixed - fortifications weapons employed in the United States . Nike sites were built during the 1950s in " rings " around major urban and industrial areas , and key Strategic Air Command bases . The number of sites constructed within varied upon many factors . Due to the short range of the original Nike missile , the Nike " Ajax " , many bases were located close to the center of the areas they protected . Frequently , they were located within heavily populated areas . The missiles were considered obsolete by the mid - 1960s , and the installations were removed .