The first siege of Gerona was the first of three French attempts to seize this city, which blocked their lines of communication between Barcelona and Perpignan (and still lies on the main road between Spain and the south of France). The French had seized Barcelona by trickery on 29 February 1808, but had not occupied Gerona. The city was not protected by strong modern fortifications. It lies on both sides of the river Oña. The larger part of the town was on the east bank, and was protected by a line of four forts that ran along a ridge just to the east of the town, with the main citadel of Monjuich at the northern edge of the ridge (this ridge still marks the eastern edge of the town). The town itself was defended by a twenty foot high medieval wall, with no ditch. The western part of the town, known as the Mercadal, was unprotected by any natural features, and so a more modern Vauban style wall had been built, defended by five bastions (modern Gerona has expanded west over the flat ground on this side of the city).
After the start of the Spanish uprising in the spring of 1808, General Duhesme at Barcelona found himself isolated from the main French armies in Spain, around Madrid. He decided that he needed to secure his direct line of communications with France, and so in mid-June left Barcelona at the head of a column just under 6,000 strong (4,300 infantry, 1,500 cavalry and eight guns). On 17 June he brushed aside a force of Spanish levies at Mongat and stormed Mataro, before reaching Gerona on 20 June.
The Spanish defenders of Gerona were badly outnumbered. The only regular troops in the town were 350 men from the Irish Regiment of Ultonia, under the command of lieutenant-colonels O’Donovan and O’Daly, and a small number of trained artillerymen. They were supported by around 2,000 armed citizens of Gerona.
Although Duhesme outnumbered the defenders, he did not have enough men to conduct a regular siege of the town, and so he decided to attempt to storm the town. His first target was the Carmen gate, at the southern end of the old walls on the east bank of the river. This was perhaps the weakest point in the defences, for it was furthest from the line of forts on the ridge to the east, but it was still within artillery range of the heavy guns in those forts. Duhesme sent one battalion to attack the southernmost of those forts – the Capuchins Fort, and another small force to attack two of the bastions of the west bank of the river, while his main attack apparently came while his aide-de-camp was still engaged in discussions with the governor and junta. Duhesme’s small force of field artillery was silenced by the guns from the forts, and the assaulting column was turned back by heavy musket fire from the walls.
Duhesme’s next attack came that night, probably at 10pm. This time three battalions from Schwartz’s Italian brigade were chosen to make an attack on the Santa Clara bastion, in the centre of the western wall. Despite some confusion during their night movement, Schwartz’s men caught the defenders of the bastion completely by surprise, and were soon established on top of bastion. However in the darkness many of their siege ladders had gone missing, and so they were unable to build up their forces on top of the walls in time to fight off a determined counterattack by the Irish regiment. The French troops at the foot of the walls then came under heavy fire from both the troops on top of the bastion and the artillery mounted in one of the neighbouring bastions.
Early on 21 June Duhesme made a second attack on one of the bastions, but this time the defenders were alert, and the French didn’t reach the walls. These three assaults cost him around 700 men. After the failure of the third attack, Duhesme decided that he was too weak to capture Gerona, and withdrew under the cover of darkness. Gerona would successfully resist a second siege between 24 July and 16 August 1808, and would not fall into French hands until the end of the seven month long third siege in December 1809.