The fall of Amiens (11 March 1597) saw the city fall to the Spanish after they used a trick to get through the city gates (Ninth War of Religion).
In 1595 the Spanish had captured Dourlens, a few miles to the north of Amiens. Amiens had been held by Henry’s opponents, but it was one of many towns to come over to his side. One of the conditions of this move was that no Royal garrison would be posted in the town. However Henry did chose Amiens as one of his depots for the upcoming campaign of 1597, so it contained a significant amount of military supplies. In the spring of 1597 the Spanish governor of Dourlens, Hernando Tello Porto Carrero, decided to take advantage of the lack of a Royal garrison to try and seize the city.
Portocarrero’s plan was to send a small advance party dressed as peasants to seize the Montrescu gate. One party was driving a wagon filled with wood, while another carried sacks of walnuts. When the wagon was directly under the portcullis, the second party spilled their walnuts. While the guards were distracted by the walnuts, the signal was given and a party of 500 Spanish soldiers that had been hidden nearby stormed the gate. The guards attempted to drop the portcullis, but it was stopped by the wagon. The Spanish were able to capture the gate, and the rest of their force was then able to break into the city.
Henry IV was dismayed by the fall of the city, but he soon recovered and was just about able to raise an army that then besieged Amiens (April-25 September 1597). This turned out to be the final major campaign of the war. The Spanish managed to raise a large relief army, but then gave up after a single assault on the French lines. Amiens surrendered ten days later. Henry was then free to move again the duke of Mercouer, the last major French nobleman who was still in arms against him. When the Royal army entered Brittany Mercouer surrendered on terms, effectively ending the Wars of Religion.