page_title: 12-inch coast defense mortar
section_title: Fire control
hierarchical_section_title: 12-inch coast defense mortar / Fire control
caption_attribution_description: Taken by me at Fort Desoto Park, Pinellas County, Florida. Olympus Camedia D-395 digital camera. CC-BY-SA-2.5 Mikereichold 00:47, 17 March 2006 (UTC)
context_page_description: The 12-inch coast defense mortar was a weapon of 12-inch caliber emplaced during the 1890s and early 20th century to defend US harbors from seaborne attack. In 1886, when the Endicott Board set forth its initial plan for upgrading the coast defenses of the United States, it relied primarily on mortars, not guns, to defend American harbors. Over the years, provision was made for fortifications that would mount some 476 of these weapons, although not all of these tubes were installed. Ninety-one of these weapons were remounted as railway artillery in 1918-1919, but this was too late to see action in World War I. The railway mortars were only deployed in small quantities, and none overseas. The fixed mortars in the Philippines saw action in the Japanese invasion in World War II. All of the fixed mortars in the United States were scrapped by 1944, as new weapons replaced them, and the railway mortars were scrapped after the war. Today, the only remaining mortars of this type in the 50 states are four at Battery Laidley, part of Fort Desoto near St.
context_section_description: The images here show another feature of the mortar pits—the data booth, part of the Coast Artillery fire control system. Personnel in this small space, with its tapered viewing slits, received the coordinates (azimuth and elevation) that had been calculated via plotting board by the battery's Range Unit as the firing coordinates for the mortars in order for them to hit their targets.
  These booths were either small, free-standing structures, about 10 feet (3.0 m) square and 7 feet (2.1 m) tall (as shown here in the topmost photos), or were built into one of the walls of the mortar pit itself (lower photo at right). The reconstructed data board in the photo at left hangs off the side of the data booth and is used to post the firing coordinates for mortars #3 and #4 in its pit (evidently the only two mortars there). The "Zone" number posted on the board refers to the size of the powder charge to be loaded for the coming shot. The top photo at right shows a decomposed set of slats (which likely used to have slates attached to them) that could have firing data chalked onto them and then be slid out of the data booth so they could be seen by the mortar crews in the pit.
  Since crews of the mortars could not see their targets, they were especially dependent on the overall fire control system, with its base end stations and plotting room, to locate and pinpoint targets for them to hit.
caption: A data booth serving a mortar pit. The display board posted azimuth, elevation, and powder charge data for the mortars.
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