 However, Mola did not hide his plans to use air force against Basque territory loyal to the Republic.Despite Basque nationalist attempts at guaranteeing no shelling on civilians, Spanish Nationalist aircraft raided Bilbao on September 25 and 26, an indiscriminate attack on its starving population that spread a blaze of outrage across the city.Oblivious to foreseeable consequences, the Nationalists resumed ferocious air strikes against the city on 4 January 1937, prompting yet another outcry of indignation and an assault on the prison-ships where right-wingers were being held.