A battlement, in defensive architecture such as that of castles, comprises a parapet of a wall, in which portions have been cut out at intervals to allow the discharge of arrows or other missiles; these cut-out portions form crenels; the solid widths between the crenels bear the name of merlons.
The term probably comes from a lost French form bastillemeni, compare modern French best/lie, from the Mediaeval Latin bastilia (towers), which derives from Italian bastire (to build), compare French bâtir; the English word, however, early became associated with battle.
The earliest example in the palace at Medinet-Abu at Thebes in Egypt takes an inverted form, and allegedly derives from Syrian fortresses. Through Assyria battlements formed the termination of all the walls surrounding the towns, as shown on bas reliefs from Nimrud and elsewhere. Traces of them remain at Mycenae, and some Greek vases suggest the existence of battlements.
In the battlements of Pompeii, additional protection derived from small internal buttresses or spur walls against which the defender might place himself so as to gain complete protection on one side. In the battlements of the middle ages the crenel comprised one-third of the width of the merlon, and the latter in addition featured a small slit. The same also appears in Italian battlements, where the merlon has much greater height and a distinctive cap.
The battlements of the Arabs had a more decorative and varied character, and continued from the 13th century onwards not so much for defensive purposes as for a crowning feature to their walls. They appear therefore in the same light as the cresting found in the Spanish renaissance. The same retention of the battlement as a purely decorative feature persists throughout the Decorated and Perpendicular periods, and not only occurs on parapets but on the transoms of windows and on the tie-beams of roofs and on screens.
A further decorative treatment appears in the elaborate panelling of the merlons and that portion of the parapet walls rising above the cornice, by the introduction of quatrefoils and other conventional forms filled with foliage and shields.
Original text from the 1911 Encyclopaedia Britannica
