page_title: Casemate
section_title: Single casemates (1889 onwards)
hierarchical_section_title: Casemate / Usage / Naval / Single casemates (1889 onwards)
caption_attribution_description: English: Imperial Japanese Navy battleship Haruna undergoes trials after her second reconstruction.
context_page_description: A casemate is a fortified gun emplacement or armored structure from which guns are fired. Originally, the term referred to a vaulted chamber in a fortress. In armoured fighting vehicles that do not have a turret for the main gun, the structure that accommodates the gun is termed the casemate.
context_section_description: A "casemate" was an armoured room in the side of a warship, from which a gun would fire.  A typical casemate held a 6-inch gun, and had a 4-to-6-inch (100 to 150 mm) front plate (forming part of the side of the ship), with thinner armour plates on the sides and rear, with a protected top and floor, and weighed about 20 tons (not including the gun and mounting). Casemates were similar in size to turrets; ships carrying them had them in pairs, one on each side of the ship.
  The first battleships to carry them were the British Royal Sovereign class laid down in 1889.  They were adopted as a result of live-firing trials against HMS Resistance in 1888.  Casemates were adopted because it was thought that the fixed armour plate at the front would provide better protection than a turret, and because a turret mounting would require external power and could therefore be put out of action if power were lost – unlike a casemate gun, which could be worked by hand.  The use of casemates enabled the 6-inch guns to be dispersed, so that a single hit would not knock out all of them.  Casemates were also used in protected and armoured cruisers, starting with the 1889 Edgar class. and retrofitted to the 1888 Blake class during construction.
  In the pre-dreadnought generation of warships, casemates were placed initially on the main deck, and later on the upper deck as well.  Casemates on the main deck were very close to the waterline.  In the Edgar-class cruisers, the guns in the casemates were only 10 feet (3.0 m) above the waterline.  Casemates that were too close to the waterline or too close to the bow (such as in the 1912 Iron Duke-class dreadnoughts) were prone to flooding, making the guns ineffective.
  Shipboard casemate guns were partially rendered obsolete by the arrival of "all-big gun" battleship, pioneered by HMS Dreadnought in 1906, but were reintroduced as the increasing torpedo threat from destroyers forced an increase in secondary armament calibre. Many battleships had their casemates plated over during modernization in the 1930s (or after the Attack on Pearl Harbor, in the case of US vessels) but some, like HMS Warspite carried them to the end of World War II. The last ships built with casemates as new construction were the American Omaha-class cruisers of the early 1920s and the 1933 Swedish aircraft cruiser HSwMS Gotland. In both cases the casemates were built into the forward angles of the forward superstructure (and the after superstructure as well, in the Omahas).
caption: Casemates on the Japanese battleship Haruna, showing their vulnerability to flooding.
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