The only way I can describe what I learned and stay family friendly is that the Spanish Civil War was a prelude and, for some, a practice session, for World War II. It did have some uniquely Spanish aspects, but many of the events in Spain happened again, soon afterward, on a more global scale.
For example, which city is this?
This was the prototype for totally destroying a city from the air, Guernica. Kind of a military experiment.
Barcelona was also systematically bombed. Mallorca was the perfect base for Mussolini's air force, a short hop over water which left no way for the population to get early warning. I don't want to go too far into this topic, because it is exceptionally brutal and tragic.
Often the reaction to these events involves art.
In Sagrada Familia is this disturbing image of an anarchist. However, the Church in Spain supported Franco and the fascist rebels, who with the cooperation of the Luftwaffe, planned and executed the destruction of Guernica.
Maybe Picasso's painting belongs in the church, too.
I can't write anymore about this.