A casemate is a fortified gun emplacement or armored structure from which guns are fired, in a fortification, warship, or armoured fighting vehicle. When referring to antiquity, the term "casemate wall" means a double city wall with the space between the walls separated into chambers, which could be filled up to better withstand battering rams in case of siege (see Antiquity: casemate wall). In its original early modern meaning, the term referred to a vaulted chamber in a fort, which may have been used for storage, accommodation, or artillery which could fire through an opening or embrasure. Although the outward faces of brick or masonry casemates proved vulnerable to advances in artillery performance, the invention of reinforced concrete allowed newer designs to be produced well into the 20th century. With the introduction of ironclad warships, the definition was widened to include a protected space for guns in a ship, either within the hull or in the lower part of the superstructure. Although the main armament of ships quickly began to be mounted in revolving gun turrets, secondary batteries continued to be mounted in casemates; however, several disadvantages eventually also led to their replacement by turrets. In tanks that do not have a turret for the main gun, the structure that accommodates the gun is also called a casemate. Etymology First recorded in French in the mid-16th century, from the Italian casamatta or Spanish casamata, perhaps meaning a slaughterhouse, although it could derive from casa (in the sense of "hut"), and matta (Latin ), "done with reeds and wickers", thus a low-roof hut without windows or other openings set in marshy place. It could also come from casa matta with in the sense of "false". However, it may have been ultimately derived from the Greek chásmata (χάσματα), a gap or aperture. Antiquity: casemate wall The term casemate wall is used in the archaeology of Israel/Palestine and the wider Near East, having the meaning of a double wall protecting a city or fortress, with transverse walls separating the space between the walls into chambers. These could be used as such, for storage or residential purposes, or could be filled with soil and rocks during siege in order to raise the resistance of the outer wall against battering rams. Originally thought to have been introduced to the region by the Hittites, this has been disproved by the discovery of examples predating their arrival,