I think few people outside Spain actually know about what happened to us by the last years of the 30s; but in a few words, we were the preamble of WWII.
The war broke out because of the military uprising in Morocco on 1936, done against the Second Spanish Republic; thus forming the two battling sides: the National side and the Republican side.
For the rest, I'll let the photos speak for me.
Street of Oviedo, 1936
Communist children demonstration to support the Republic - Barcelona, 1936
Bombs falling on the village of Gandia, 1937
Kids making the Roman salute after discovering the Cibeles statue, at the end of the war - Madrid, 1939
Republicans making the Socialist salute on a local train - Madrid, 1936
Young Basque militia defending the Spanish Republic arrested. Some of them are kids. - Vitoria, 1936
One of the main streets of the capital city, during the war - Madrid, 1938
Three years after the end of the war, the Spanish dictatorship greets the German ambassador - Madrid, 1942
And if anyone wants to see videos, here's part of a Republican report informing on the resistance in Barcelona. It's in Spanish, but the footage is original.