Fortress Tower

a defensive structure, a constituent part of fortress walls in antiquity and the Middle Ages. Fortress towers were built of brick, stone, and wood and were placed at the corners of the walls and along lengthy rectilinear sections. Extending somewhat beyond the plane of the wall, the fortress towers were usually circular, semicircular, rectangular, or polygonal in form; their diameter was up to 20 m, and their height was sometimes one and a half to two times greater than that of the wall. The towers were intended for observation, for the protection of troops engaged in enfilade firing along the fortress walls, for the security of the approach routes and for the defense of the gates. They also served as cover for troops and as a strong point of the defense. With the appearance of artillery the fortress towers became more massive, their height was diminished, and they were adapted for the firing of artillery pieces. With the development of artillery in the 16th and 17th centuries the fortress towers began to be replaced by bastions.