The siege of Castro-Urdiales (22 March-12 May 1813) saw the French recapture a port that had fallen to a joint Anglo-Spanish force in the summer of 1812, but only after suffering a series of setbacks largely caused by underestimating the difficulty of the task.
Early in 1813 Napoleon had placed General Clausel in command of the Army of the North, and given him a series of detailed orders explaining how he was to regain control of northern Spain. Most of these could only be achieved once reinforcements from the French Army of Portugal had arrived, but the capture of Castro-Urdiales, only fifteen miles west/ north-west of Clausel’s base at Bilbao, seemed to be achievable. Castro-Urdiales was the only fortified port then in Anglo-Spanish hands, and a useful base for the Royal Navy’s cruisers in the area.
The task of taking the port would turn out to be more difficult than the French had realised. The town itself was then restricted to a single rocky headland, which was cut off from the mainland by a strong defensive wall 20 feet, carrying 20 guns. There was also a medieval castle on the far end of the spit. There was also a force of 3,000-4,000 Spanish guerrillas under Gabriel de Mendizabal and his subordinate Campillo close by ready to take advantage of any French mistake.
On 21 March Clausel left Bilbao with most of Palombini’s Italian division and one French battalion. At this point he believed that the port had old and badly maintained walls, and that it could be taken by a simple assault. However on 22 March, when he finally reached the port, he realised that this wasn’t the case. His chief engineer, Vacani, reported that he would need 6 siege guns and 6,000 men to take the port.
Clausel’s initial plan was to carry out the attack anyway. However news then reached him that his base at Bilbao was threatened, so he left, taking his French battalion with him. Palombini was left in the area, but camped at San Pelayo (possibly the small village of that name twenty miles to the south, although that does seem a long way from the port). On 24 March Mendizabal attacked the camp at San Pelayo, triggering a battle in which both sides suffered heavy casualties.
Soon after this Clausel sent General Rouget, with two battalions to join Palombini. Clausel then returned to the front himself, but decided that he didn’t have enough men or guns to risk the attack. Palombini was ordered to burn the ladders and fascines that had been prepared for the siege, and move west to raise the Spanish blockade of Santona, a few miles further west along the coast.
Palombini carried out his orders, getting small arms and ammo into the besieged port. He also passed on orders to General Lameth, commander of the garrison, for him to prepare to place six heavy guns on ships, along with siege supplies, ready for the next attempt to capture Castro-Urdiales.
This didn’t come until late April. On 21 April Foy reached Bilbao with his division, and orders to take command of the siege. A few days later Sarrut’s division also arrived. He also had Palombini’s Italians, Aussenanc’s brigade and the garrison of Bilbao, a total of 16,000 men. On 24 April Foy left Bilbao with his own, Sarrut’s and Palombini’s men, a total of 11,000 men, and he arrived outside on the same day.
Foy gave Palombini the task of blockading the port, while he went to hunt for Mendizabal, who was believed to a few miles further west, on the road to Santona. Foy established his siege headquarters at Cerdigo, two miles west of Castro Urdiales on the coast.
On 29 April Foy drove off Mendizabal’s weak force at Ampuero (eight miles to the west/ south-west of Cerdigo, in the river valley that runs north to Santona). He then opened up communications with Santona, moving supplies into the town. Lameth was ordered to move the siege train he had prepared to Islares (below his base at Cerdigo) on the first day where the bay was clear of British warships (in particular the sloops HMS Lyra, HMS Royalist and HMS Sparrow, all under Captain Bloye, which were based off Castro). Unfortunately for the defenders, these ships were distracted by the need to watch Bilbao, and while they were absent Lameth was able to ship his guns and supplies into place on 4 May. More heavy guns were moved across land from Bilbao, but arrived late.
Foy then prepared for the siege itself. Sarrut’s division was posted at Trucios (seven miles to the south of the port), to cover the siege. Two Italian battalions were sent to Portugalete (at the mouth of the river leading to Bilbao), to keep the road to Bilbao open. Foy’s own division and three Italian battalions were allocated to the actual siege work.
The port was garrisoned by 1,000 men from Longa’s regiments of Iberia, commanded by Colonel Pedro Alvarez. He put up a determined defence, but was very badly outnumbered and outgunned, and once the heavy guns were in place the result of the siege was inevitable. He was supported by naval gunfire from the British ships, and by the fire from a heavy gun that Captain Bloye had mounted on the island of Santa Anna (probably now built into the much larger modern harbour), just outside the harbour, but their combined efforts were unable to stop or much delay the progress of French siege works.
Foy built three batteries on the hills that overlook the port. Two were completed on 6 May, and opened fire on 7 May. These two batteries had been built too far from the walls, and had little impact. One was soon knocked out by British gunfire. The third battery was much closer to the walls. It was ready by 10 May and opened fire on 11 May. Within two hours the guns in this third battery had created a breach 30 feet wide.
It was now clear to Alvarez that the port could no longer be held. On the afternoon of 11 May part of the civilian population was evacuated onto the British warships and the garrison prepared to withdraw into the castle. The British also withdrew the gun on Santa Anna, as it would have fallen into French hands if left there much longer.
At 7.20pm Foy launched an attack on the walls. Eight French flank companies attacked the now 60ft long breach, while eight Italian flank companies attacked a low part of the wall near the Bilbao gate. Both attacks succeeded, and the Spanish were forced to retreat to the castle. This was only a temporary measure, to win time for an evacuation. Two Spanish companies defended the steep steps up to the castle gates, while the rest of the garrison embarked on the British ships.
A last force of 100 men was left in the castle with orders to set fire to the magazines and throw the guns into the sea. Early on 12 May the French stormed the castle, killing some of this final force, but most escaped by boat.
Both sides claimed to have suffered low losses in the siege - the Spanish only 100 men, Foy only 50, but the losses were probably rather higher. Most of the Spanish garrison escaped by sea, and moved to Bermeo, where they joined Longa, and many took part in the battle of Vittoria. The three French divisions were less well used - only Sarrut was present at the decisive battle of the year.
A History of the Peninsular War, Volume VI: September 1, 1812 to August 5, 1813: Siege of Burgos, Retreat of Burgos, Vittoria, the Pyrenees