Renaissance Warfare and Weapons - Defending Against a Siege
Castles, with their thick, tall walls, were built for defense but with the advent of gunpowder they were no longer effective. For example, the army of Ferdinand and Isabella conquered the Moorish strongholds in Granada. These strongholds had held off attackers for centuries but the use of gunpowder and cannons proved no match for the old way of defending yourself.
Realizing that the old methods of building fortifications had to change, the Italian architect Leon Battista Alberti during the fifteenth century postulated that walls be “built in uneven lines, like the teeth of a saw”.
A few towns began building fortresses with this new style but the vast majority of rulers paid no attention to this new theory of protection. Things changed dramatically when Charles VIII invaded Italy with only 18,000 men and horse drawn siege engines. This tactic proved so effective that he could defeat virtually and city or state no matter how well it was defended.
It became obvious that a new style of fortress was needed to withstand these new styles of attacks.
New defense strategies:
The old high and relatively thin walls of the castles were easy targets for cannons. It was obvious that the most effective way to protect the fortress walls was to increase the thickness of the walls and to have varying angles to lessen the likelihood of a direct (square) cannon hit. Walls were lowered and earth was used to thicken them in front and in back. The old square towers familiar in the castles were changed into triangles.
The new fortress designs eventually led to the “trace italienne” style of fortification. Developed in Italy during the late fifteenth and early sixteenth centuries in response to the French invasion of the Italian peninsula. This new style of fortification was designed to withstand the use of cannons that so easily destroyed traditional fortifications.
To withstand an attack by the new weapons the walls were built lower and thicker. The new design also included the building of “bastions”. A bastion projects out from the main wall of a fortification and is situated at the corners of straight walls. The bastion allows the defenders to cover different angles and to cover adjacent bastions with protective fire. Bastions provide covering fire, often from multiple angles. The need for cover fire at differing angles led to the design of the “star” shaped fortress.
These star shaped defenses proved to be very difficult to capture. The cost to build these new styled fortresses was incredibly high. In a strange twist of fate the town of Siena spent so much money building the style of fortress for protection that it didn’t have enough money to maintain their army so it lost the war anyway.
Around the mid 1500’s this new style of fortress spread from Italy into the remainder of Europe. The demand for Italian engineers knowledgeable in the design of these new fortresses was especially high in war torn countries like the Netherlands, France and Spain.
These new fortresses could hold over 10,000 men and were designed to withstand a series of sieges. A fortress holding over ten thousand soldiers meant that the attacking armies had to be aware of the risk of a counter attack too.
In the late 1600’s Marshal Vauban, a French military engineer made improvements on the new fortress design. He added slopes so that attackers could no longer be protected when they got close to the fortress (these slopes are called glacis).A glacis is an artificial slope of earth placed in front of the wall of a defended position. The slopes are constructed to keep attackers under the fire of the defenders. Without the glacis, on natural ground level, troops attacking any high structure achieve a degree of protection from its fire when they get close to it. Raising the ground to form a glacis allows the defenders to keep the attackers under fire from a bastion or a parapet.
Vauban also improved on the bastion design to allow the attackers to be enfiladed. This meant they were designed to be able to shoot at various angles. An attacker is “enfiladed” if the defenders can shoot straight down the line of attack. For example if the defender can shoot down the length of a trench then the trench is “enfiladed”.
Vauban also added trenches as defense mechanisms.
Fort McHenry in Baltimore, La Citadelle in Quebec City and Fort Ticonderoga in New York are all examples of the Vauban fortress design.