On Franco's orders, the Condor Legion bombed the Basque city of Guernica on Monday, April 26, 1937. This attack was considered the first major raid in the history of modern warfare on the defenseless civilian population, the motives are still a subject of controversy. It resulted in a virulent international condemnation. It was at this moment that international attention turned to the involvement of Nazi Germany and fascist Italy in the conflict. This was the first time that German aviation action resulted in a large number of civilian casualties. This destruction received wide media coverage and created an international perception of German participation in the Spanish conflict. Guernica was also a harbinger of what was going to be done against civilian areas in the Spanish Civil War and future conflicts.
In addition to the potential for gaining combat experience, various strategic initiatives were devised and first tested as part of the Luftwaffe involved in this conflict. Theories on strategic bombing were first developed by the Luftwaffe, with the first demonstration of the carpet of bombs during the Asturian campaign in September 1937. As the fighting progressed in March 1938, the Italian pilots, under the command of Feldmarchall Hugo Sperrle, were involved in thirteen of the raids on the city of Barcelona, using incendiary bombs and gas bombs. These raids led to the death of thousands of civilians.
It is now known that during the Experiment Stuka 38 people died in 1938 because the Nazis wanted to test whether their dive bombers would be able to transport and drop bombs weighing 500 kilos – double the normal amount, which prevented them from filling up their gas tanks completely. And so they chose four small and unarmed Spanish villages, close to their air base, to destroy. In just a few months these tactics would be used by the Nazis on a new front across Europe during World War II.
There are numerous reason's given for Hitler's support of Franco, however, the main reason consisted of the Condor Legion, an adjunct of the Luftwaffe. The Condor Legion provided the Luftwaffe the opportunity to develop and perfect tactics of aerial warfare that would fuel Germany's blitzkrieg through Europe during 1939 and 1940. This point of view is supported by the testimony of Hermann Goring, who became Reichsmarchall of the Luftwaffe, at the trial at the Nuremberg International Military Tribunal. When asked about the decision to use the Luftwaffe, he stipulated:
" When the civil war broke out in Spain, Franco sent a call for help to Germany and asked for support, especially air. We must not forget that Franco's troops were stationed in North Africa and that he could not get his troops across, because the fleet was in the hands of the Communists or, as they called themselves, time, the "legitimate revolutionary government in Spain". The main factor was to transport his troops to Spain. The Führer thought about it. I advised him to support (Franco) in all circumstances, first, to prevent the spread of communism in this region and, secondly, by this opportunity to test my young Luftwaffe . "