page_title: Seacoast defense in the United States
section_title: Modernization
hierarchical_section_title: Seacoast defense in the United States / World War II / Modernization
caption_attribution_description: English: This image, provided courtesy of the Coast Defense Study Group (CDSG), shows a 16-in barbette-mounted gun in a casemated position. These were the largest guns mounted by the U.S. Coast Artillery Corps. This emplacement features a steel shield that wraps around the gun carriage, protecting it from nearby blast effects.
context_page_description: Seacoast defense was a major concern for the United States from its independence until World War II. Before airplanes, many of America's enemies could only reach it 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 U.S. 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 U.S. 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.
context_section_description: The outbreak of war in Europe in September 1939 and the Fall of France in June 1940 greatly accelerated U.S. defense planning and funding. About this time a severe lack of design coordination resulted in the Iowa-class battleship being unable to use the Mark 2 and Mark 3 16-inch guns, and a new gun design was required for them. With war on the horizon, the Navy released the approximately 50 remaining guns, and on 27 July 1940 the Army's Harbor Defense Board recommended the construction of 27 (eventually 38) 16-inch two-gun batteries to protect strategic points along the U.S. coastline, to be casemated against air attack, as were almost all of the older batteries by this time.
  The 16-inch guns were only the top end of the World War II program, which eventually replaced almost all previous coast defense weapons with newer (or remounted) weapons. Most of the 12-inch long-range batteries were casemated and served through the end of the war. Generally, each harbor defense command was to have two or three 16-inch or 12-inch long-range batteries, plus 6-inch guns on new mountings with protected magazines, and 90 mm Anti Motor Torpedo Boat (AMTB) guns, which were supplemented with 37 mm or 40 mm anti-aircraft guns. In addition to the proposed 38 new 16-inch (406 mm) batteries with a range of 25 mi (40 km), eleven new 8-inch (203 mm) batteries with a range of 20 mi (32 km) and 87 new 6-inch (152 mm) batteries on high-angle shielded mountings with a range of 15 mi (24 km) were projected. All of these batteries had two guns each with heavily protected magazines and plotting rooms and casemated guns (except the 6-inch guns had shielded mountings). Additionally, about 32 8-inch MkVIM3A2 railway guns were deployed. In most cases replacing existing harbor defenses, with wartime changes noted, fortifications were planned for the harbor defenses of:
  East coast
  Portland, Maine
  Portsmouth, New Hampshire
  Boston, Massachusetts
  Cape Cod Canal (16-inch not built)
  New Bedford, Massachusetts (no additional heavy guns)
  Narragansett Bay
  New York City
  Long Island Sound
  Southern New York
  Delaware River
  Chesapeake Bay
  Charleston, South Carolina (16-inch not built)
  Gulf coast
  Key West (no additional heavy guns)
  Pensacola, Florida (no additional heavy guns)
  Galveston, Texas (no additional heavy guns)
  West coast
  San Diego, California
  Los Angeles, California
  San Francisco, California
  Columbia River (no additional heavy guns)
  Puget Sound (no additional heavy guns)
  Cape Flattery, Washington
  Dutch Harbor, Alaska (biggest guns were 8-inch)
  Kodiak, Alaska (biggest guns were 8-inch)
  Sitka, Alaska (no heavy guns)
  Seward, Alaska (no heavy guns)
  Other U.S. possessions or overseas
  Honolulu
  Pearl Harbor
  Kaneohe Bay
  North Shore of Oahu (biggest guns were 8-inch and 240 mm howitzers)
  Balboa, Canal Zone (no additional heavy guns)
  Cristóbal, Colón (16-inch not built)
  San Juan, Puerto Rico
  Roosevelt Roads Naval Station (biggest guns were 8-inch)
  Trinidad (no heavy guns built)
  Jamaica (not built)
  Bermuda (biggest guns were 8-inch)
  Argentia, Newfoundland (no heavy guns)
  With CONUS and the Caribbean less threatened as the war progressed, about 21 16-inch gun batteries were completed in 1941-44, but not all of these were armed. Three new 12-inch long-range batteries and five 8-inch batteries (mostly in Alaska) were completed and armed, and about 65 6-inch batteries were completed, but only about 45 of these were armed. Some batteries on Oahu were completed with two 14-inch triple turrets from the sunken Arizona and eight 8-inch twin turrets removed from Lexington and Saratoga rather than the designed guns. As the areas of combat became more distant from the U.S. and as naval threats were essentially removed, defending harbors against ships became a low priority, and as the new coast defense batteries were completed, almost all of the older seacoast guns were scrapped to become new weapons. Many soldiers of the Coast Artillery were transferred to field artillery, anti-aircraft, or even infantry duties. When the war ended, it was soon decided that seacoast defense guns were n
caption: 16-inch casemated gun.
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