COUNTERFORT. A form of buttress used for the strength ening of walls of mediaeval fortifications. It was found that with the introduction of cannon as siege weapons in the i 5th century, the ordinary types of masonry walls backed with earth, were not sufficiently strong to stand battering by artillery. They were there fore strengthened with buttresses or counterforts from the inside of the wall. Later the counterfort often took the form of an arched gallery, built behind the wall under the rampart. (See further FORTIFICATION and SIEGECRAFT.) An outwork of a system of fortifica tions built in front of the face of a bastion or ravelin to protect it from breaching fire (Fr. Contre-garde). A counter-guard usually consisted of a V-shaped work with two ramparts meeting at an angle and an open gorge. (See further FORTIFICATIONS AND SIEGECRAFT.)