Siege of Amiens (1597)
The Siege of Amiens between 11 March and 25 September 1597, was a battle fought during the Franco-Spanish War (1595-1598) as part of the French Wars of Religion and the Anglo-Spanish War (1585–1604). The Spanish initially captured the city, only to lose it to the French later in the year.
Prelude
Spain had intervened regularly in the French Wars of Religion in favour of the Catholic League, most notably in the Siege of Paris (1590) and the Battle of Craon in 1592. However only in 1595 was war officially declared between the two countries by the new King Henry IV of France, who had the year been received into Paris to be crowned following his conversion to Catholicism.
The Spanish take Amiens
In 1597, Hernando Tello Porto Carrero, the Spanish governor of the city of Doullens taken in 1595, proposed a plan to Archduke Albert, sovereign of the Habsburg Netherlands to take Amiens by surprise. Only weeks after the disaster at the Battle of Tielenheide in Brabant, Cardinal Albert agreed, and assigned 7000 men infantry and 700 cavalry to Governor Porto Carrero.
The plan was to hide 500 infantry and horsemen in small groups close to the city. Governor Tello sent 14 or 16 men dressed as peasants into the city and divided them into three groups. On the morning of 11 March, these men entered the Gate of Montrescu. The first group carried sacks of walnuts and apples, which "accidentally" capsized at the city gate. When French guards grabbed the nuts, the "peasants" brought out pistols and overpowered the guards. One guard dropped the gates, but it could not close, because the peasants had unhitched a wagon filled with wood. The hidden 500 Spanish infantry and the cavalry time enough to storm into the city. Within two hours, the city was under Spanish control.
Because of this action, the people of Amiens still have the nickname Walnut eaters.
The French besiege Amiens
Henry IV of France, who had spent the winter in Paris, was awakened that night at the Louvre and by morning had donned his armor. He quickly brought an army of 4,000 French, English, and Swiss infantry and 700 French cavalry under Charles de Gontaut, duc de Biron to Amiens.
This army cut off the provision lines from Doullens and lay siege to the city.
The Spanish were taken by surprise by the speed of the French reaction and were not prepared for a siege. Many civilians were chased from the city. Meanwhile, preparing for a long siege, the French camp grew in size and even two hospitals were built. The Spanish launched many unsuccessful attempts against the siege works.
On 4 September, the French attacked the city and Porto Carrero was killed. He was succeeded by Girolamo Caraffa, Marquis of Montenegro. Caraffa was warned that a large Spanish relief army under Peter Ernst I von Mansfeld-Vorderort was under way, which reached Amiens on 20 September. Charles, Duke of Mayenne was able to convince Henry IV and Biron not to confront the relief army in open battle, but to remain in the entrenchments. This strategy was successful, because a Spanish attack on the French camp was repelled, inflicting many casualties. Von Mansfeld decided that the situation was hopeless and withdrew.
Girolamo Caraffa now started negotiations for the surrender of the city, which was signed on 25 September.
Source
Memoirs of Henry the Great, Volume 2 by William Henry Ireland