The cruel siege of Siena

When the army of Europe’s most powerful monarch besieged the Tuscan city in 1554, it took terror and hunger to achieve what cannon and arquebus could not, as William E Welsh explains.


The wrath of Charles V – the Holy Roman Emperor and Europe’s most powerful monarch – showed clearly around Siena during the early spring of 1555. Over the past four centuries, the Tuscan city – the capital of the republic of the same name – had grown to become one of the Continent’s economic and cultural centres, known for the quality of its governance as well as for the beauty of its architectural and artistic treasures.

But now it was entering its second year under siege, with Spanish, German, and Italian soldiers of the emperor’s besieging army occupying a string of camps and small forts that encircled it. The once-beautiful surrounding countryside, which formerly boasted magnificent tracts of mature forest, was denuded of trees, which the Habsburg emperor’s soldiers had used as fuel, or in the making of forts.

A 16th-century painting by Giorgio Vasari depicts the surprise attack on Siena on the night of 26 January 1554. Although the attack failed, imperial troops secured a toehold outside Porta Camollia (pictured), the city’s heavily fortified northern gate.

In an effort to stave off starvation, the French defenders of the city had previously turned out thousands of noncombatants, so that there might be fewer mouths to feed. The besieging troops, however, had refused to grant them passage through their lines. As a result, corpses were piled up in no-man’s land, and those who had somehow survived clung precariously to life amid the squalor beneath the walls of the city that had once been their home.

The condottiero commanding the siege army had gradually tightened his blockade of the city the previous autumn. By the beginning of the year, Siena had been without supplies for several months. Starvation strangled both the garrison and those unfortunate civilians who were still behind the city’s formidable walls.

The fight for Tuscany

When the electors of the Holy Roman Empire chose King Charles I of Spain in 1519 to serve as the new emperor, it further enhanced the grip he had on western Europe, and which began with the generous inheritance he had received three years earlier. Following his election, Charles – who adopted the imperial name of Charles V as his main title – controlled the Netherlands, the Habsburg lands in Germany and Italy, and the Spanish kingdoms in the western Mediterranean.

The powerful position of the Habsburg dynasty hemmed in France. Yet the Valois monarchs of France remained more determined than ever to contest Habsburg hegemony, not just on France’s north-eastern frontier, but also in Italy, where the two dynasties had waged war since 1494 in a string of bloody conflicts known as the Italian Wars.

As the wars progressed, the principal objective of France was the wealthy Duchy of Milan, controlled by the Habsburgs. The French already controlled Savoy, Piedmont, and Saluzzo, west of Milan. To the south lay a number of small states of north-central Italy, including the republics of Florence, Siena, and Lucca, over which Charles held sway. If the French could gain control of one of these republics, it would afford them a new base in Tuscany from which to threaten Milan.

The Holy Roman Emperor Charles V (above) had no intention of allowing France’s King Henry II (below) to roll back his previous successes in the long-running Italian Wars.

When the French king, Francis I, died in 1547, his second son, Henry II, succeeded him. Henry had close ties to Italy through his wife, Catherine de Medici, whom he had wed in 1533, when she was 14. Francis I had earlier been captured and imprisoned at the French defeat at the Battle of Pavia in 1525. In order to gain his freedom, Francis turned over his two eldest boys, Francis and Henry, to serve as hostages in Madrid for a time.

During the four years that he and his brother spent in captivity in a dank cell in Madrid, Henry developed a lifelong hatred of the Habsburg ruler. For this reason, he was keen to go to war against Charles V – but he bided his time as he waited for the right opportunity.

Opposition to a citadel

The city of Siena lay 40 miles south of Florence and 116 miles north of Rome. Like Genoa, it was a hub of commerce and banking. Situated on a western spur of the Chianti mountain range, the city was enclosed by more than four miles of high walls. On maps, the enclosed portion of the city resembled a church bell, with the narrowest part in the north and the broadest part in the south. Although the walls lacked towers at regular intervals, some of Siena’s fortified gates boasted towers of their own.

Charles first intervened in the internal affairs of Siena in 1530, in order to restore civil order as a result of infighting among rival factions. In 1550, frustrated that the Sienese seemed to ignore his edicts, he sent Don Diego Hurtado de Mendoza, a veteran of the Habsburg victories at Pavia and Tunis, to serve as governor. Mendoza had orders to disarm the Sienese and collect taxes from them on a regular basis. Finding the Sienese unwilling to billet his soldiers, Mendoza drew up plans to construct a hilltop citadel to the west of the city in which to house his troops.

In September 1550, a Sienese delegation appealed to the emperor to halt construction of the citadel. Charles flatly refused. After this rebuff, the Sienese approached the French king, Henry II, seeking military assistance if they rebelled against the emperor. The following year, while Sienese diplomats were conducting talks with the French king, a war erupted between Henry II and Charles V for control of the Duchy of Parma. Ottavio Farnese, the Duke of Parma, had appealed to the French king for aid in resisting the emperor. The war ended in 1552 in a French victory that inspired the Sienese to appeal to Henry for protection as well.

A French protectorate

A vintage map highlights how France was hemmed in by the dominions of the Habsburg Empire during the reign of Charles V.

Siena called out its militia in the summer of 1552. When the Sienese captain Enea Piccolomini arrived at the gates of his native city on 27 July with 3,000 armed militiamen, urban patriots opened the gates to them. The 400 Spanish troops in the city at the time retreated from the piazza, where they had been skirmishing with the patriots, to the partially completed citadel.

Mendoza was in Rome at the time, and he rushed back to the city. Having received the emperor’s approval to negotiate terms of surrender, the imperial commander obtained permission from the Sienese to depart with his troops. On 5 August, they withdrew 75 miles south to the port of Orbetello, on Tuscany’s Tyrrhenian coast.

Henry declared Siena a French protectorate. He sent Piero Strozzi, the hero of the Parma War, with 5,500 French forces to the republic to defend nearly two-dozen key positions, including towns and frontier castles, against a Habsburg invasion. The French king also sent the noted military engineer Paul de Thermes to assist the Sienese in improving the defences of their capital.

A fanciful depiction of theSiege of Siena shows cannon and large arquebuses in the foreground being transported to the siege lines by pack horses.

Thermes recommended the construction of five bastions at or near Porta Camollia, the city’s northern gate – the most direct route from the Republic of Florence, which was a key ally of the emperor. The Sienese left standing two antiquated towers situated north of the gate. All able-bodied citizens, male and female, began working on the bastions and other defence projects.

Surprise attack

Charles felt compelled to respond to the French presence in Siena, for he could not afford to suffer another reverse in Italy akin to the one he had experienced in Parma. The campaign faltered initially, when a Spanish army from Naples became bogged down in February 1553 besieging the strategic fortress of Montalcino, 25 miles south of the Sienese capital. The Neapolitan army withdrew four months later, when an Ottoman fleet threatened Naples.

Charles entered into a secret agreement with Cosimo de Medici, the Duke of Florence, in November 1553 whereby he agreed to reimburse the duke for all of the expenses he might incur leading a fresh invasion of the Republic of Siena. Cosimo subsequently appointed veteran condottiero Gian Giacomo Medici, the Marquis of Marignano (no relation to the Florentine Medici family), to lead the invasion. The Florentine army initially consisted of 2,000 Florentine troops and 5,500 German mercenaries.

On the night of 26 January 1554, Marignano launched a surprise attack on the Sienese capital, hoping to capture it in a coup de main. Although the attack failed, the imperial troops secured a toehold outside Porta Camollia by capturing the northernmost of the two medieval towers – where Marignano’s army began entrenching and constructing gun emplacements. The two sides would duel with their artillery over the coming months.

Marignano also sent detachments to secure other parts of Siena; for that reason, he lacked enough troops in the spring of 1554 to undertake a formal siege. He began constructing fortified camps around the city to head off French troops and supplies, but this would prove to be a slow process owing to the siege army’s chronic shortage of manpower.

The search for advantage

In early 1554, Strozzi began planning his own move: a counter-offensive against the Florentine Republic in the hope of winning a victory that would end the invasion of Siena. To direct the garrison while Strozzi was leading a French field army against Florence, Henry II dispatched the veteran general Blaise de Monluc to Siena.

As it turned out, the only accomplishment of Strozzi’s offensive that spring was that he managed to rendezvous with French reinforcements from Lombardy while threatening Florence’s northern frontier. In mid-July, he returned to Siena – where the supply situation was becoming increasingly desperate – before marching off to the Chiana Valley, about 30 miles east of the city, in the direction of Arezzo. This put his army astride the Florentine republic’s line of communications with Rome. He hoped that this would draw Marignano, who had shadowed his army throughout his counter-offensive, into a decisive battle.

Both armies had swelled in numbers with the prospect of a pitched battle. Strozzi now had 15,000 men against Marignano’s 18,500: the two sides would have been more equally matched if Strozzi had received 4,000 French reinforcements from Corsica as promised, but they had failed to arrive as planned.

On 2 August, Strozzi launched a spirited attack on Marignano’s imperial army near Marciano Castle – in the heart of the Chiana Valley – but veteran Spanish cavalry routed the French horse and then returned to the field of battle to assist the imperial pike and shot troops in vanquishing the French foot soldiers. Strozzi suffered 8,000 killed, wounded, and captured. The imperial victory put an end to any hope the French may have had of winning an open-field victory against the forces of the Habsburg emperor.

After the Battle of Marciano (also known as the Battle of Scannagallo), Marignano had once again to parcel out his forces to support operations against multiple objectives in the Republic of Siena. When he returned to the siege lines at the Sienese capital, his army had dwindled even more as a result of desertions, sickness, and disease. He soon found himself with no more than 7,000 troops in the trenches. Fearing that the siege might fail, he sent an urgent plea in September 1554 to Cosimo de Medici requesting more infantry, trained artillerymen, and pioneers.

The terror factor

After his defeat at Marciano, Strozzi transferred his headquarters to the hill town of Montalcino, south of Siena, and left Monluc in charge of the city’s defence. Marignano tightened his blockade of the city in the months that followed by establishing additional fortified encampments to the south and east of the city. This eventually enabled his troops to cut off any supplies at all from reaching the beleaguered garrison.

The last wagon train of supplies rolled into Siena on 18 September. Shortly afterwards, Monluc took the drastic step of turning out thousands of so-called ‘useless mouths’ from the city in order to make the remaining supplies last as long as possible. Of the 25,000 noncombatants in the city, he intended to send away 10,000.

Henry II sent Piero Strozzi (above), the hero of the Parma War, to defend Siena against
a Habsburg invasion. For his part, Charles V entrusted operations to Cosimo de Medici (below), his principal ally in Tuscany.

For Marignano, it was a golden opportunity not only to terrorise the poor souls sent away, but also those still inside the city. On 3 October, he ordered his troops to hang any soldiers or male civilians found either trying to bring food into the city or attempting to depart for the safety of the countryside. To ensure that his soldiers carried out this harsh sentence, Marignano promised a bounty for each enemy soldier or male civilian who was hanged.

Although Marignano allowed the first group of 1,000 civilians to pass through his lines, he decided that from that point forward he would allow no more civilians to do so. As a result, those who were driven out of the city slowly starved to death in no-man’s land, in full view of the soldiers and citizens who remained in Siena.

‘Rapid bombardment’

At that point in the siege, Marignano decided to try to knock a breach in the eastern walls of Siena through which his crack Spanish and German arquebusiers could fight their way into the city. In November 1554, he moved ahead with preparations for what he termed a ‘rapid bombardment’ – in which he would mass his guns to concentrate their fire on a specific section of the city’s walls. The plan proceeded with the utmost secrecy. To aid the effort to breach the walls, Cosimo arranged in late November for the transfer of 13 additional cannon from other strongholds in southern Siena. However, inclement weather and the difficulty of transporting heavy guns across rough terrain meant that the additional artillery did not arrive until the first week of January 1555.

Having been informed on 7 January that the additional guns were nearing Siena, Marignano issued orders the following day for the Spanish and Florentine pioneers to level a section of the forward slope of the Ravacciano Hill, which overlooks the eastern gate of the city known as Porta Ovile. The plan called for oxen to haul the guns as close as possible to the artillery site under cover of darkness on the night of 9/10 January. After that, troops would manhandle the guns into position by dawn. The two captains of the artillery batteries had orders to commence firing once the sun was up.

An unexpected reverse

Marignano chose as the target for the bombardment part of an extension wall that enclosed the Church of San Francesco, which was situated just south of Porta Ovile. Unfortunately for the imperialists, however, Monluc learned of the plan on 9 January from a captured enemy soldier. To respond to the threat, Monluc ordered his troops to position demi-cannon on Fortino di Santa Croce, a bastion on the north-east corner of the city, to enfilade the imperial batteries at Ravacciano.

As it happened, the imperialists only managed to get nine guns into action on the morning of 10 January. With the rising sun behind them illuminating the walls of the city, the artillery crews began firing initially at the base of the specified section of the wall. Their intention was to try to batter the base of the wall in the hope of collapsing it. When this proved impossible, they shifted their fire at midday to the middle of the wall, hoping it would prove easier to destroy.

The imperial gunners toiled throughout the day in the face of sniper-fire from French arquebusiers on the city’s eastern battlements, as well as accurate fire from the demi-cannon at Fortino di Santa Croce.

Although they fired a total of 260 rounds from their bronze guns, the imperial gunners failed to collapse the wall, or even to batter an opening in it. The French claimed afterwards to have dismounted six of the nine enemy cannon. The operation, which had been planned and awaited with great hope for two months, had been a complete failure.

Forced to surrender

Crestfallen residents of the city pray for relief from imperial tyranny in an etching after Pietro Aldi’s 19th-century painting The Last Hours of Sienese Liberty.

Marignano had no choice now but to wait until starvation compelled the garrison to surrender. Little did he know, but the civilian leadership in the city wanted Monluc to surrender – for they feared a brutal sack if the imperialists succeeded in fighting their way into the city. Cosimo desired a successful end to the siege, and for that reason he continued to send not only Spanish and German troops, but also Florentine militia to assist Marignano in making sure that neither supplies nor a relief column reached the city.

By the late winter of 1555, the majority of the French troops and Sienese militia inside the city were either too weak from hunger or too sick to play an active role in defending its circuit of walls. Anxious to end the suffering of their people, the Sienese leadership sent a delegation to Florence, which Marignano allowed through his lines, to negotiate directly with Cosimo de Medici. He, in turn, consulted with Charles V.

Monluc refused to participate in the negotiations, because he did not want the embarrassment of having the French garrison surrender directly to the Habsburg emperor. Still, the Sienese leadership accepted the terms of surrender in early April.

The terms called for the Sienese to acknowledge that they were subjects of the emperor. If they did this, Charles said, they could govern themselves provided they obeyed his judgments and decrees. The Sienese also had to dismantle all of the outerworks that they had constructed and make no further enhancements to the citadel. As for the French, Charles V allowed them to turn over control of the citadel to the Sienese and depart with full honours of war.

The Sienese signed the surrender on 17 April 1555. Monluc marched out four days later with his troops and a small number of Sienese rebels who faced death or imprisonment if they stayed behind. The rebels relocated to Montalcino, where they continued to hold out until the end of the war.

Four more years

The combination of terror and starvation had forced the city’s unconditional surrender after 15 months. Yet, while the Spanish held the capital and had a tenuous hold on the northern half of the republic, the French and Sienese rebels controlled the southern half of the republic from Montalcino.

The so-called Last Italian War would drag on for four more years. During that time, Charles abdicated (in 1556) and retired to a monastery in Spain. His eldest son, Philip II, ruled the Spanish Habsburg domains, which included the Kingdom of Naples and Duchy of Milan, while Charles’ brother, Ferdinand I, ruled the Austrian Habsburg domains.

France and Spain finally ended the conflict on 3 April 1559 by signing the Peace of Cateau-Cambrésis – bringing down the curtain after more than 400 years on the Republic of Siena. In that agreement, the French relinquished all of their claims in Italy and returned all captured territory, except for the Piedmontese region of Saluzzo, to Spain. In the aftermath of the treaty, Spain would remain the dominant power in Italy for the next 150 years.

Philip II was not the only one to reap the fruits of victory. The Medici also benefited immensely. The king of Spain owed a vast sum of money to Florentine bankers, and for that reason he ceded the Republic of Siena to Cosimo, further consolidating the family’s power. In 1569, Siena was finally merged to become part of the new Grand Duchy of Tuscany – a monarchical state that would exist, albeit with interruptions, until 1860. Cosimo, naturally, served as its first ruler.

Further reading:

  • Thomas F Arnold, The Renaissance at War (Cassell, 2001).
  • Simon Pepper and Nicholas Adams, Firearms and Fortifications: Military Architecture and Siege Warfare in Sixteenth-Century Siena (University of Chicago Press, 1986).
  • Christine Shaw and Michael Mallett, The Italian Wars 1494-1559: War, State and Society in Early Modern Europe (Routledge, 2018).
All images: Wikimedia Commons