19 August 1936,
The Battle of Irun entered a decisive phase. Since Gipuzkoa was maintained by the Republic, the city was a strategic goal. Mola sent a column from Navarra. Some 6,000 soldiers were on the Bidasoa front, 3,000 on each side, but Republicans were much worse armed. To help the Carlists, through Occitania they sent from Catalonia a train full of weapons, but the French authorities kept him standing, even if they were left. The city stayed for a month, while the Francoists bombed. Irun rose from 18,500 to 7,700.
Source:
Mario Salegi, Die in Irún. (Elkar).