The Mechanics of Fortresses An historical journey in the evolution of military science and technique for the construction of the fortresses of Palmanova, Gorizia and Gradisca d’Isonzo.

Gorizia Castle

Video

Episode 1 (duration 2 min 37 sec) The journey was long and tiring (watch the video) – After a long journey, an English noblewoman of the late 1800s arrives in Gorizia. A grand tour of wonders to discover the Castle and the city of Gorizia, among parks and stately buildings, continuing then towards Gradisca d’Isonzo and Palmanova.

Episode 2 (duration 3 min 17 sec) I’m Edmond Halley (watch the video) – Edmond Halley recounts his experience in Gorizia: after passing through the Porta Leopoldina, an imposing castle dominates the Borgo. Its strong point is its position on the hill, which prevented enemy artillery from approaching.

Episode 3 (duration 3 min 58 sec) Project of the Castle Tower (watch the video) – The Lady enters the Castle. Walking through the large rooms, she begins to tell its history, its evolution and its characteristics. On the desk, a sheet of paper with the project of a tower, signed by Edmond Halley.

Episode 4 (duration 3 min 22 sec) Gunpowder is more efficient (watch the video) – Halley, from his study, and the Lady, from inside the fortress, describe the improvements to the castle’s fortifications, made over time to better suit the development and effectiveness of new firearms.

Studies by Alberto Prelli

The castle of Gorizia dates back to the 11th century and underwent modifications over time. It had the perfect characteristics of a medieval castle. It was located high on a hill, had a wall in stone blocks, with a pair of tall towers. Inside the walls there were residential buildings and a keep consisting of a high quadrangular tower, which allowed a three hundred and sixty degree view of the surrounding territory. The fortification was suitable to withstand the traditional siege engines of the time, catapults and trebuchets, which threw projectiles, generally made of stone, with an arched shot to overcome the high walls and hit houses and warehouses inside, rather than knocking down the walls.

Already in the first half of the 14th century, bombards appeared on the battlefields, which, initially, were used against weak targets. They were neither large nor reliable, they overheated, with the risk of breaking and killing the gunners. These guns fired horizontally with a limited range, so for a useful impact on the walls they had to be placed very close to the target, with the risk of being damaged, or captured, by a sortie from the besieged. The bombards certainly had the psychological effect of the din that terrified the enemy.

Even in the 16th century experts considered that placing cannons less than 100 meters away was unsafe, and more than 280 meters too far to be effective.

Given these drawbacks, traditional castle fortifications could suffice without major upgrades, so catapults, trebuchets and other siege machines continued to play their role until the 15th century.

However, during the second phase of the Hundred Years’ War in France in 1430 large cannons caused serious damage to the walls of a manor, so much so that the garrison capitulated.

Although fortresses, positioned in advantageous places and beyond the reach of cannons, could resist, after the mid-1400s the artillery pieces of the major states could reduce most vertical defenses to rubble in a few days.

For example, in the siege of Constantinople in 1453, Mehmet II used a new devastating and very expensive weapon: a gigantic cannon. It was 8 meters long, weighed 50 tons, took 100 oxen to transport, and fired stone projectiles weighing 1 quintal, with a diameter of 3 meters. With this weapon he managed to knock down the walls of the city. In this case, however, the lack of adequate response by the besiegers and the fact that only the finances of a great monarch could support the cost of building, transporting and using such a piece of artillery are evident.

From the mid-1400s, the effectiveness of gunpowder was gradually improved, stone projectiles were replaced by lead or iron ones, which caused greater damage to medieval walls, and, finally, metallurgy progressed, making it possible to cast larger cannons with more penetrating power.

Under the rule of the Republic of Venice, which had conquered Friuli in 1420, the fortifications of the castle of Gorizia were improved to make them more suitable for the development of new firearms. The high tower of the keep, an easy target for artillery, was demolished, and a large round tower was built on the walls to support the weight and recoil of heavy cannons. Reinforcing the curtain walls and thickening the towers, to absorb the impact of enemy projectiles, were useful measures, but they remained within the scope of traditional vertical defenses, which could only delay the effects of the shots of a battery of cannons.

As early as 1440, Leon Battista Alberti suggested that a fortification would be more effective if built in a broken line, like the teeth of a saw. He also imagined that the star shape was the best and offered greater protection, using crossfire.

In 1500, Count Leonardo of Gorizia died and the castle passed to Emperor Maximilian I of Habsburg.

In 1508, the emperor and the Serenissima entered into conflict. Gorizia was attacked by Bartolomeo d’Alviano, commander of the Venetian army, and the castle surrendered in a few days.

After 1514, the city and fortress returned to the emperor, who continued the adaptation works. A polygonal fort with three pointed bastions was built around the castle, as envisaged by the new theories of military architecture.

In the 17th century, the castle was used as a prison and barracks. The fortification was further updated.

In the early 18th century, at the request of Emperor Leopold I, the English Queen Anna Stuart sent the scientist Edmond Halley on a diplomatic mission. The aim was to map the Dalmatian coasts of the upper Adriatic and identify a large port where vessels could dock. Halley also examined Trieste, which he deemed unsuitable.

From there he went to Gorizia, where the county captain Gio Filippo di Koblez was working on the defensive works that surrounded the village and the castle. Halley, who also practiced military engineering, according to the testimony of the priest Giovanni Maria Marussig, began designing a new bastion, connecting it with a long and thick wall towards Castagnevizza to another bastion, which joined with another wall to the Porta Leopoldina, built in 1660.