Casemate

casemate [′kās‚māt]

(ordnance)

A bombproof structure used as a powder magazine, gun emplacement, or the like.

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casemate

A vault or chamber in a bastion, having openings for the firing of weapons.

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Casemate 

(1) An area in a fortification for the protection of personnel from direct hits by artillery shells and aerial bombs. Prototypes of casemates were known in ancient times. The perfection of artillery and the appearance of aviation provided the impetus for the widespread development of casemates. Depending on its purpose, a casemate is called a combat, observation, living, or ammunition casemate. It is customary to call all those modern fortifications with casemates as casemated, distinguished from open fortifications.

(2) An armored enclosed area on ships for the installation of guns, the storage of shells, and the protection of personnel from enemy fire. Casemates were widely used on artillery ships in the second half of the 19th century and the first half of the 20th century. Because of changes in warship design (in particular armor plating), casemates have almost completely lost their importance.

(3) Before the 20th century, an isolation cell in a prison located in a former fortress, primarily for the detention of political prisoners.