During the War of the Pyrenees (1793–1795), which was effectively the Pyrenean front of the First Coalition's war against the First French Republic, Someruelos was sent to the front lines at Guipúzcoa as commander of arms in the first battalion. On 10 October, he was promoted to colonel of infantry. Leading over 1,000 grenadiers, he was one of the officers in charge of reconnaissance during the Spanish campaign of 1794, in which he commanded two divisions of advance troops, often under enemy fire. he was made a brevet brigadier by April 1795.