Chemin-des-Rondes

A protected passageway along the top of a scarp wall that could be covered by a low earthen parapet or a masonry parapet built onto the top of the scarp wall. Also, ground immediately in rear of crenellated detached or semi-detached scarp walls where troops stood to deliver their fire through loop-holes. This feature of permanent fortifications had fallen out of use during the latter half of the 17th century, but was revived during the first half of the 19th century by Prussian and German engineers who developed the polygonal system of fortification. Unlike the bastion system in which one element of the trace defended another the polygonal system relied on long straight walls that were flanked by casemated caponnieres. These long sections of wall could not generally be seen or defended by any other element of the trace; this characteristic condition of the polygonal trace prevented troops firing from the parapet of the enciente rampart from defending the main ditch. To remedy this situation crenellated detached and semi-detached scarp walls were applied to the enciente and outworks to advance defending troops to the scarp where they could direct their fire downward onto hostile troops in the main ditch.

American engineers, following the lead of French engineers, generally rejected the polygonal system as it was practiced in Germany, but did adapt some of that system's features when they offered some perceived advantage. Both Fort Gaines, Alabama and Fort Clinch, Florida were enclosed by crenellated semi-detached scarp walls and the chemin-des-rondes characteristic of the polygonal system. In both cases the interior lines of the chemin-des-rondes between the bastionnets at the angles were not broken by permanent masonry traverses; their chemin-des-rondes were accessible from the forts' parades through passageways cut into the sides bastionnet posterns (which ran under the rampart) immediately in rear of each bastionnet.  Fire delivered from the chemin-des-rondes through the loop-holed scarp wall defended the glacis, covered way, and crest of the counterscarp while the foot of the scarp was defended by the bastionnets' flanks. This arrangement was much less expensive than previous coastal fortifications constructed with hollow casemated walls, but only provided one tier of guns firing en barbette from the terre-plein of the rampart.

January, 2003

August, 2005