Fortifications

Historians and military strategists have said that defensive tactics start with the building plans. Certainly, the defenders’ options are affected by the “trace” (ground plan), and a well laid-out castle is easier to defend than one with design flaws. As it had altered strategy for the attacker, the introduction of gunpowder made the job of the military architect considerably more difficult. In addition to withstanding the assaults of a besieging army--and the pounding of siege batteries--the fortification’s trace had to maximize the effect of the garrison’s own artillery. These (sometimes conflicting) goals broke down along the following lines.

First, a rampart that was spacious and low-lying enough to provide a stable platform for artillery had to be built.

Second, the walls had to maintain a low enough profile to make it difficult for the enemy to hit, while still being strong enough to resist the blows of the enemy shot. Further, a wall and ditch arrangement had to be formidable enough to deter attempts at escalade.

Lastly, a trace had to be so arranged that it left no “dead ground” through which an enemy might reach the rampart without coming under the defensive fire of the keep’s weapons. Satisfying more than one of these requirements was not an easy task for the medieval architect.

Probably the most significant advance in fortification architecture was the development of the “bastion” in the late Fifteenth and early Sixteenth, and its ascendancy over the round tower so typical of the Medieval period. Bastions were projections shaped like an ace of spades, positioned where older forts would place round towers. They were usually no higher than the walls from which they sprung, and had battlements and crenellations running around their tops. Bastions were sometimes hundreds of feet across.

The bastion neatly met most of the requirements discussed above. Bastions had wide flanks, making it possible for the garrison to concentrate withering cross-fire on troops trying to approach the wall. Too, the angular salient--the meeting of the two faces of the bastion-- eliminated the patch of dead ground which had existed in front of the circular medieval tower. Fields of fire were opened for the flanks of neighboring bastions, which meant that individual towers no longer were on their own when it came to close-range defense. Finally, the defenders could mount considerably more cannon on the walls of a bastion than they could on a circular tower of equal size (and cost).