The Nationalist Army, under Alfonso Beorlegui, captured the city of Irún cutting off the northern provinces of Gipuzkoa, Biscay, Santander, and Asturias from their source of arms and support in France.

[7] Colonel Beorlegui's force was smaller, but it included 155 mm artillery, German light tanks, Junkers Ju 52 bombers, and a 700-man bandera from the Spanish Foreign Legion.

Both Germans and Italians carried out heavy air strikes over Irun and Hondarribia (Fuenterrabía) on a daily basis, at the same time dropping pamphlets over the towns threatening to repeat the massacres of Badajoz.

The peak of the battle occurred at the convent of San Marcial, which was defended by Asturian miners and militia who threw dynamite and rocks when they ran out of ammunition.

[8] Thousands of civilians and militias fled in panic for their lives across the Bidasoa border to France as the rebel far-right forces entered the town.