What happened
Military officers rebelled against Spain's republican government, triggering a long civil war that quickly drew in foreign support, ideological solidarity, and experimental warfare.
Why it matters
Spain became one of the clearest arenas in which fascism, anti-fascism, revolution, counterrevolution, and non-intervention collided before the wider European war. It belongs here as both symptom and rehearsal.
Notes
Use this as the main proxy-war and ideological-polarization anchor.