The combats of Guernica (2 and 5 April 1813) saw a French column force the Spanish guerrillas to abandon their HQ in Biscay, but the majority of the Spanish troops were able to escape, reducing the value of the success.
The attack on Guernica came in the middle of the siege of Castro-Urdiales (22 March-12 May 1813), a port on the coast west of Bilbao that had been captured by a joint Anglo-Spanish force and was being used as a minor British naval base. The first attempt to retake Castro-Urdiales had failed because the French underestimated the difficulty of the task. General Clausel, the French commander in the north, decided to withdraw Palombini’s Italian Division from the siege while he put in place plans to move siege guns along the coast to take part in the second part of the siege.
Palombini returned to Bilbao after three forced marches. Two days later Clausel ordered him to move east to attack the HQ of the Biscayan Junta and guerrillas at Guernica, just over 13 miles to the east of Bilbao. A second French column, made up of two battalions from the 40th Line, was to attack from Durango, nine miles to the south of Guernica, and attack the Spanish from the rear.
Palombini’s troops attacked Guernica on 2 April. As he advanced towards the town the Spanish pulled back, while also calling reinforcements to the area. They abandoned Guernica, but them made a stand on the far side of the town. Palombini attacked this new position, but the second French column never arrived from Durango, and he was forced to withdraw. Palombini claimed to have only suffered 80 casualties during this fighting, but at least five officers were wounded in the fighting, and the true casualty figures were probably higher.
Over the next couple of days Palombini was finally joined by the troops from the 40th Line. With his reinforcements in place he attacked the Spanish at Guernica a second time on 5 April, and this time forced them to retreat. His hope was to trap the retreating Spanish between his troops and a brigade that had been sent to block the coast road near St. Sebastian, 35 miles to the east. However this plan failed. The Biscayan troops escaped from the trap by heading south into the hills of their home province. The troops from Guipuzcoa (the next province to the east) were in more danger as they attempted to head home along the coast road, but they were warned in time. Some escaped south into the hills, while others were picked up by British warships at Lequeytio (Lekeitio) and Motrico (Mutriku) and taken back to Castro-Urdiales.
As a result Palombini failed to take any prisoners. He moved south into the hills and captured the magazines at Aspeytia (Azpeitia) and Azcoytia (Azkoitia) , and then returned to the main Bayonne road at Bergara on 9 April, placing him nearly 30 miles to the east of Bilbao. He was thus absent when the Spanish attempted to capture Bilbao (10 April 1813), taking advantage of Clausel’s absence and the weakness of the French garrison left behind. Although this attack failed, once again the French were unable to capture many of the Spanish as they retreated.