Aftermath

Although primitive and unformalized, Celtic fortification had made some significant advances. The Celts had well understood the fact that a fortified place could enable a small body of defenders to resist a superior attacking force. They did not invent, but understood and developed several fundamental principles of fortification, notably the vital importance of taking advantage of height, of natural defense, and of the efficient combination of ditch/rampart. They put in practice the essential principle of command, a law of fortification by which the vertical elevation of one work over another or above the surrounding country provides the defenders with superior fire positions, and enables the fortification to dominate an area by virtue of its height. The broch, for example, would later reappear in the history of British fortifications, albeit in varying forms: Roman towers, medieval keeps and wall-towers, post-medieval tower houses, and 19th-century Martello towers. Although designed to serve different purposes, the broch and all these later structures basically use elevation as a safety device. The Celts also applied with success the so-called principle of defense in depth, characterized by several lines of defense and outworks. Defense in depth is a military tactic that in modern terminology is referred to as elastic defense or deep defense. Its purpose is to delay rather than prevent the advance of an attacker, buying time and causing additional casualties by slowly yielding space. Defense in depth requires that a defender deploy his fortifications in several lines. When attackers breach one line, they continue to meet resistance as they advance, and one captured work or line does not mean the collapse of the whole defense.

Owing to the combination of fortifications and warrior-heroes, the British Celts were convinced that they could defeat any invader, even the Romans, of whom much had been heard in the last century of the pre-Christian era.

Despite their elaboration and the titanic efforts of the multitudes which went into their creation, Iron Age hill forts, were of little use against the superior Roman material culture and military power. In 55 B. C. the Romans set foot on British shores. They were repulsed but returned in a. d. 43. They came bearing — no doubt without realizing it — the accumulated lore of a variety of cultures reaching back over 2000 years. The Romans had acquired considerable technical and military knowledge, they had their own ideas on how to deal with other people, and they had developed their own concepts about military architecture. After a. d. 43 a new and much clearer phase of British fortification began.

Part 2