The town was bombed on 26 April 1937. Gernika was the first town to be targeted by a bombardment:
The bombardment proved the perfect testing ground for the newly created German air force, the Luftwaffe. Although allegedly the official objective was to destroy the small Rentería Bridge to prevent Basque troops retreating towards Bilbao, the huge proportions of the attack demonstrate it was also one of the best ways to demoralise the troops, weaken the resolve of civilians and thus precipitate the subsequent collapse of the Northern Front.
As we said, Gernika was bombed on Monday, 26 April 1937, market day. There was quite an atmosphere of unease at the time, particularly in the wake of the recent bombardment of the nearby town of Durango, some 30 km from Gernika. Despite this the market went ahead as usual and, although it is difficult to establish any precise figures in this regard, a total of approximately 10,000-12,000 people were in Gernika that day. At 16:20 h, the bells of the Santa María church rang out to warn the local population of the approach of enemy aircraft. Most of the planes formed part of the German "Condor Legion", along with a smaller number from the Italian "Aviazione Legionaria". The aerodromes used as a base for the bombing mission were located in Vitoria, Burgos and Soria. After the warning had sounded, the people of Gernika ran to seek refuge in a number of shelters built for this purpose, where they stayed for almost four hours until the bombing stopped. The attack was incessant, with barely any intervals between the bombing waves, and the tactics used in the raid were as follows:
More than 85% of the town was totally destroyed.