Guernica, by Pablo Picasso (1937)
On this day in 1937, the Germans began testing their Luftwaffe on the small, non-beligerant town of Guernica in Spain's Basque region. The attack began in broad daylight, lasted for hours, was totally unprovoked, killed hundreds of civilians, and destroyed the town. Spanish leader Franco approved the attack.

Pablo Picasso's work commemorating this tragic event was completed two months later.