Battle of the Baztan Valley The Battle of the Baztan Valley was fought between 23 July and 1 August 1794 during the French Revolutionary War , between a French force from the Army of the western Pyrenees commanded by Bon - Adrien Jeannot de Moncey and the Spanish forces led by Don Ventura Caro . The French army drove the Spanish from their defenses , then followed the valley northward to the Atlantic coast . The Spanish forces holding the coastal defenses were compelled to surrender or flee . Background . Sans Culotte Camp . General of Division ( MG ) Jacques Léonard Muller was appointed commander of the French Army of the western Pyrenees on 5 October 1793 . The year 1793 saw no major battles in the western Pyrenees , though a number of skirmishes occurred between French and Spanish forces . On 5 February 1794 , Lieutenant General ( LG ) José Urrutia y de las Cases attacked the Sans Culottes Camp , a fortified hilltop near Hendaye . A French division led by MG Louis Dubouquet repelled the 13 , 000 Spanish infantry , and their 700 supporting cavalry and artillery . Spanish casualties numbered 335 while French losses were unknown . June operations . On 3 June , a 2 , 300 - man French brigade led by General of Brigade ( BG ) Lavictoire stormed Casa Fuorte , a position at the Izpegi Pass ( Col d ' Ispeguy ) , 13 . 5 km airline km west of Saint - Jean - Pied - de - Port . The 1 , 000 defenders , including a battalion of the Spanish " Zamora " Infantry Regiment , three companies of the " Aldudes " Rifles , and the French Émigré " Légion Royal " , lost 94 killed and wounded , plus 307 captured . Other Spanish defenses on Izpegi Ridge and the Maya Pass were also overrun that day . On 23 June , Captain General Don Ventura Caro with 8 , 000 infantry and 500 cavalry and artillery unsuccessfully assailed Mount Calvari near Bera ( Vera ) . The Spanish lost 500 killed and wounded , plus 34 captured . The French defenders lost 30 killed and 200 wounded . Battle . Monte Argintzo . The June fighting gave the French army a foothold in the Baztan Valley . Muller ordered the Spanish positions in the Baztan to be assaulted and assigned MG Moncey to carry out the operation . On 10 July , BG Antoine Digonet and 4 , 000 French troops attacked the " Zamora " Infantry and the " Légion Royal " on Monte Argintzo ( Mont Arquinzu ) . The peak is located at , 10 km south of Elizondo in the Baztan . The outnumbered defenders lost 314 casualties including LG Marquis of Saint - Simon badly wounded . After the battle , the republican French massacred 49 royalist French prisoners . Baztan . Moncey had his own and two other divisions under his supervision . Beginning on 23 July , Moncey ' s divisions attacked the Spanish entrenchments in the Baztan . The valley includes the towns of Elizondo , where the Baztan river turns from southwest to west and Doneztebe where the river turns north and becomes known as the Bidasoa . By between 27 and 30 July , the Spanish defenses were overcome and Moncey turned his divisions northward to follow the Bidasoa to the Atlantic coast . The number of French and Spanish killed and wounded is unknown , but the French captured 200 Spaniards and four artillery pieces . Emerging from the mountains on 1 August , Moncey fell upon the Spanish coastal defenses from the flank and rear with 12 , 000 men , capturing the San Marcial heights southeast of Irun and Hondarribia ( Fuenterrabia ) . Trapped by the French maneuver , LG Don Vicente de los Reyes surrendered with 2 , 000 Spanish soldiers , 300 cannon , and five colors . The French suffered 600 casualties . Result . Moncey ' s offensive completely unhinged the Spanish defensive position behind the Bidasoa River . The French went on to seize the port of Pasaia ( Pasajes ) on 2 August . A bigger prize fell on 3 August when San Sebastián surrendered to the French with 1 , 700 Spanish prisoners and 90 cannon . French losses were negligible . The town of Tolosa fell to Moncey soon afterward .