As long as weapons remained relatively primitive, permanent fortifications predominated. The art of fortification developed in earliest times with the building of earthworks made up of layers of mud, sticks, rocks, and the like. These soon were developed into walls, then into palisades and elaborate wooden stockades. In the Middle East walled cities appeared very early. Those of Mesopotamia had walls of mud or sun-dried brick built to withstand invaders. The citadel, a fort or fortified section within the city, also appeared early. Phoenician cities were strongly walled and offered sturdy resistance to Assyrian, Persian, and Macedonian attackers. Major developments in permanent fortification were made by the Romans, who constructed walls along the Danube and Rhine and in England (e.g., Hadrian's Wall). Some of these had elaborate systems of watchtowers, with provisions for garrisoning men along the walls. In E Asia the famous Great Wall of China was an even more ambitious undertaking of the same type.
To overcome advances in fortification, siegecraft (see siege) evolved, and devices such as battering rams, scaling ladders, catapults, and movable towers appeared. As siegecraft became more effective, walls were made higher and thicker—often 30 to 40 ft (9.1–12.2 m) thick. The Romans, with their engineering skill, also developed field fortifications in their camps. However, with the breakdown of Roman authority and the increase in raids and incursions by invaders from the North and the East, fortification on the grand scale was largely replaced by local fortifications.
In the Middle Ages, when raids and petty warfare were customary, the typical fortifications were town walls of masonry, great citadels within the cities, and castles. The Crusades helped further the development of fortifications. Similar structures were used in the chaotic warfare of feudal China, India, and Japan. In the West many castles and citadels, notably those of the Moors in Spain, were defensible against all but a long siege.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.