Bilbao was bombed by German aircraft with five deaths. Republican aviation managed to knock down one German aircraft and two out of six crew members managed to save it by parachute. One of them fell in a working-class neighborhood and was lynched.

The bombings caused discomfort and the mass demonstrations led by the UGT battalions broke out in the prisons where Francoist prisoners were. 224 were executed.

The Basque Government stepped up this insurrection and prevented the death of more Franco prisoners.