The siege of Siena (January 1554-April 1555) was one of the longer sieges of the Italian Wars, and was one of the last attempts by the pro-French party in Italy to counter Imperial and Spanish power in Italy. The siege lasted for fifteenth months, but eventually starvation forced the surrender of Siena, which then became part of Cosimo de Medici's Duchy of Tuscany.
Background to the Siege
The Republic of Siena was one of the more turbulent Italian states. Siena was a long-standing Republic, but was also officially part of the Holy Roman Empire. As was often the case in the Italian republics the city was often disturbed by factional struggles and it had always been a difficult place to rule.
In the early 1540s the city was ruled by a council, the Nova, supported by a political group called the Noveschi. This group had been expelled on several occasions, and had most recently returned in the 1520s. At about the same time Charles V had put a Spanish garrison in the city in an attempt to impose order.
In 1545 the people of Siena rose up against the Imperial commissioner Juan de Luna and the Noveschi. The Spanish and the Noveschi were driven out of the city. Cosimo de Medici, ruler of Florence, managed to prevent any excesses in the city. Charles then sent Francesco Grassi from Milan in an attempt to arrange a compromise. He failed, and in 1547 the citizens took up arms again. This time they accepted the protection of the Pope, exluded the Noveschi from any share in the government and protested against the presence of any foreign garrison in the city. Once again Cosimo managed to negotiate a settlement, and in September a Spanish garrison returned to the city.
In October Diego Mendoza, the Imperial ambassador to Venice and later to Rome, arrived at Siena. He received an impressive reception as the representative of Charles V, but he soon wasted this good will. In November 1548 he restored the Noveschi and the Council of Forty, but also insisted that half of the members should be picked by himself. In 1549 he disarmed the people, and announced that Charles intended to build a fortress outside the city. This was portrayed as an attempt to protect Siena, but was seen within the city as an attempt to overawe it.
The proposed fortress was a serious mistake. Not only did it alienate the citizens, work on it proceeded so slowly that it was of no value when the Sienese revolted once again.
In 1552 Siena revolted against Imperial rule. The revolt was organised at Chioggia near Venice in a meeting that included the Cardinal of Ferrara, Prince Ferrante Sanseverino of Naples, Orazio Farnese, Niccolo Orsini, the Strozzi family (exiled from Florence) and the French Ambassador. The plotters hoped to take advantage of a series of threats to the Imperial position, including a Turkish threat to Naples and fighting in Piedmont that distracted Ferrante Gonzaga, Prince of Mantua, Imperial Governor of Milan.
On 17 July 1552 a force of French and Italian troops under the command of Louis de Lansac and the Sienese Aeneas Piccolomini. The Spanish garrison was forced to surrender, but Cosimo de Medici managed to prevent the revolt from spreading further across Italy by mediating an agreement with the rebels. Siena was to be a free city under Imperial protection and no foreign troops were to enter the city, On 5 August the citizens destroyed the half-built Spanish castle.
The French soon broke the agreement, moving troops into the city. The Cardinal of Ferrara took over the administration of the city, generally acting in the French interest and the fortifications of the city were reinforced.
Imperial forces made a first attempt to recapture Siena in January 1553. Pedro Alvarez de Toledo, Viceroy of Naples, landed at Livorno, while Garcia de Toledo, the Viceroy's second son, led his army from Naples into Tuscany and took up a position on the border. Cosimo de Medici gave some guns to the Imperial troops and stopped the French from moving reinforcements through Florentine territory. This attack stopped when the Viceroy died at Florence. In the aftermath of this failure Diego de Mendoza was recalled to Spain while Gonzaga's authority was greatly reduced.
Cosimo de Medici now changed his attitude. Previously he hadn't wanted to see Gonzaga or Mendoza gain too much authority in northern Italy, but now that they had been removed or reduced in power he was free to act against Siena. On 25 November 1553 he made a secret treaty with Charles V in which he agreed to recover Siena for the Emperor. He was motivated by the activities of Pietro Strozzi, who had gained French support and was attempting to raise a revolt against Medici rule in Florence.
On 7 January 1554 Strozzi entered Siena. Eleven days, on 18 January, he left to examine the defences of the Republic. This left the city somewhat vulnerable, and on the night of 26 January Florentine troops managed to capture the Porta Camollia. They were unable to take advantage of this early success and were soon expelled, but this marked the start of the serious fighting.
The attacking forces were commanded by Gian Medecino, Marquis of Merignano, a successful artillery commander who conducted a methodical siege.
Strozzi was a much more flamboyant commander, adept at mobile warfare. He was aware that he needed more troops and so sent messages to France asking for help and reinforcements. Henry II of France decided to send Blaise de Monluc to rule the city, while Strozzi would remain in command of the field army.
Strozzi still had to actually meet up with the French reinforcements. He achieved this with a daring raid that took him deep into Florentine territory. He broke through the siege lines and headed north, crossing the Arno just to the west of Florence. He then joined up with the reinforcements coming from the north and moved towards the lower reaches of the Arno. He was nearly trapped between Pisa and Piatoia, but managed to escape south towards Piombino. Here he met with his first disappointment, discovering that his brother Leone had been killed while fighting at sea. From Piombino he joined up with more reinforcements then moved east, before entering Siena with 17,000 reinforcements.
Strozzi's next plan was for an attack on Florence. He led his field army north-east towards Arezzo, with the aim of moving north-west from Arezzo along the Arno towards Florence. This plan ended in failure. Merignano was able to trap Strozzi in the Chiani valley, south of Arezzo, and then defeated him in battle at Marciano (2 August 1554). Strozzi escaped, but his army was destroyed.
This allowed Merignano to concentrate on the siege of Siena. It was soon clear to Monluc that food supplies were crucial. Half way through the siege he let his landsknechts go in order to reduce the drain on resources.
A more dramatic step was take in February 1555 when he expelled 4,400 'useless mouths' from the city. Monluc later admitted that he would never again witness anything quite so frightful. After eight days trapped outside the city half of the 4,400 had died and the other half had managed to escape.
By the spring of 1555 food had almost run out and starvation was widespread. Eventually the Sienese decided to surrender. Monluc refused to take part in the capitulation and left before the final surrender. The city surrendered on 21 April 1555.
In 1557 the new Spanish king, Philip II, gave Siena and most of the Republic's territory to Cosimo, and it became part of the Duchy of Tuscany. A number of coastal towns were retained by the Spanish and were ruled from Naples as the 'Stato dei Presidi' or the 'State of the Garrisons'..
The fall of Siena didn’t end the war. A group of Sienese families escaped to Montalcino in the mountains, where they held on until 1559, but they never threatened to overthrown the earlier arrangements.