The Mechanics of Fortresses A historical journey through the evolution of military science and technology for the construction of the fortresses of Palmanova, Gorizia and Gradisca d’Isonzo.

The Fortress City of Palmanova

Video

Episode 1 (duration 3 min 04 sec) The Last Kiss (watch the video) – The noblewoman arrives at the star-shaped fortress city of Palmanova. She enters the carriage through one of the three monumental gates and heads toward the Cathedral. After admiring it from the outside, she walks inside the church.

Episode 2 (duration 2 min 13 sec) Giulio Savorgnan, engineer (watch the video) – In Friuli the Venetians wanted to create a new fortress, Palmanova, that could contain a large number of militia and artillery. Giulio Savorgnan led the project. To define the plan, he started from the most effective measurement of the royal cannon: 350 meters.

Episode 3 (duration 3 min 38 sec) The Impregnable Fortress (watch the video) – The Lady describes the effective and innovative defensive structure of Palmanova: three concentric circles of walls, bastioned wall, lunettes, bastions and ravelins, the moat and the monumental gates, the only three access points to the Fortress.

Episode 4 (duration 3 min 26 sec) A Star in the Plain (watch the video) – The star that Giulio Savorgnan had drawn on paper became reality and remained unchanged over time. The defensive structure, however, improved further, thanks to the massive modernization works ordered by Napoleon Bonaparte starting in 1806.

Studies by Alberto Prelli

Although casting in bronze, rather than iron, significantly reduced the weight of large cannons, only large-caliber artillery pieces were truly effective.

In 1519, Nicolo Machiavelli wrote that there was no wall thick enough that artillery could not ruin it in a few days.

By the late sixteenth century, even additions to medieval defenses, both due to the increased power of cannons and improved siege techniques, became inadequate.

Only compact triangular bastions offered any real security. Innovative bastioned citadels and fortresses arose in central Italy to house and counter the power of artillery. This “modern” or “Italian” form quickly spread throughout Europe.

The military engineer Francesco Lucarelli, author of the bastioned walls of Valletta in Malta in 1566, was convinced that it was impossible to defend a stronghold against an army equipped with artillery without having bastions.

In the first twenty years of the 16th century, the Venetians in Padua began to experiment with new construction criteria to defend themselves from increasingly effective artillery, from circular bastions to the subsequent polygonal ones, designed and built by Michele Sanmicheli between 1540 and 1547.

Between 1567 and 1570, the pentagonal citadel of Antwerp arose. But to fortify an entire city, a long-term vision was needed. Because such an undertaking could not be started in the face of imminent danger.

In the late 16th century, the use of artillery required large, low and powerful embankments to house heavy cannons and absorb the enemy’s projectiles.

Thinking of a bastioned wall, which would embrace a pre-existing city, in addition to a lot of money, involved high social costs, such as the destruction of large areas of the suburbs, which were located just beyond the medieval walls.

Which did not happen in the case of Palmanova, a city/fortress of foundation, which was built on an open plain, free from a pre-existing walled city. Thus the solutions to be adopted could be the most innovative.

Venice, after having secured the western border of the state, decided in 1593 that the time had come to do the same for the eastern one. The moment was favorable, because the Archduke of Austria, who owned part of Friuli, was engaged in war against the Ottomans. The new stronghold would have had the purpose of facing possible Turkish incursions and controlling the borders with the archducals.

The commission of five superintendents, supported by engineers and soldiers, was sent to Friuli to search for a suitable site to build a stronghold.

Giulio Savorgnan, head of the Office of the Fortresses of Venice, was in charge of drawing up the project. In outlining the plan of the fortress, he started from the fundamental measurement of the most effective range of the “royal cannon”, that is, 200 paces (350 meters). This allowed, with crossfire, each bastion to defend the one next to it and its curtain. At the time, we can consider the “royal cannon” to be the bronze cannon that fired 50-pound balls (25 kilograms). Its maximum range, but not in terms of effectiveness, was around a kilometer, it weighed about 2,100 kilograms and 10 pairs of oxen were needed to move it.

Savorgnan determined the cost of a single bastion, not knowing how many would need to be built. Perhaps he thought of the Nicosia solution with eleven bastions, which he had already built. The Venetian Senate was thinking of a fortress with 10 bastions. In the end, after all the calculations, the choice fell on a star fortress with 9 bastions.

Savorgnan designed the fortress with arrowhead bastions (like an “ace of spades”) and connected them with the curtain walls. The result was a non-agon with bastions protruding from its vertices, so that they could defend each other with crossfire. Knights were erected on the curtain walls, from which cannons and culverins could keep the batteries of the besiegers away. The entire circuit was further protected by a wide and deep moat. The city could be entered from three entrances, located in the center of the curtain walls.

In the mid-17th century, the Serenissima judged the time had come to further strengthen the fortress, creating another 9 triangular embankments, the ravelins, which were built beyond the moat in correspondence with the curtain walls. The first to be completed were those in front of the access gates, which have always been the weakest point of any fortress. Countermine tunnels were also dug and walled, which passed under the ravelins and went towards the countryside.

But the art of fortification added another chapter to the design of Palmanova. Napoleon Bonaparte, already in his first visit in 1797, understood both the strategic importance of the stronghold on the Austrian borders and its weakness in relation to the new resources of artillery. The Treaty of Campoformido concluded the very brief stay of the French and every project was shelved.

Immediately after the French reconquest of Friuli and its annexation to the Kingdom of Italy in 1806, Napoleon decided to subject the Palmanova war machine to massive works. The most visible imprint were the 9 large pentagonal earthworks, the lunettes, in line with the bastions, surrounded by a dry moat. These extended even further towards the countryside and could have kept enemy batteries further away, avoiding destruction of the city and military buildings. A system of casemates, traverses and underground tunnels was built to support the lunettes. Inside the fortress, powder magazines and barracks of modern design were also built.

This was the last and profound sign traced in the book of the fortification history of Palmanova. Soon the mobility of the armies, the power of the weapons and the aviation made the fortresses obsolete. Fortunately, Palmanova has preserved its defensive structures almost intact. Offering the visitor the possibility of moving, immersing himself in the history of military architecture, not in a virtual way, but in a real and tangible way.