ABSTRACT
As gateways are basically large openings they can weaken the incumbent masonry, and from the strategic point of
view they provide obvious targets of assault. They therefore have to match the strength of the walls, do minimal damage to the structure of the brickwork, and provide a defendable means of access and exit. The jambs were strengthened by vertical pilasters or buttresses, and the wooden lintel of an ordinary doorway was usually replaced by an arch, which distributes the pressure from the wall above more evenly and allows for a wider span. The flanking buttresses could develop into gate-towers protruding above the wall, which could in turn be surmounted by battlements and contain chambers and stairways for the use of the guardsmen (eg Ishtar gate at BABYLON).
