The origins of this food fight are a little murky, but the most popular explanation begins with an attempted rape, a vengeful decapitation, and a torched castle. In the Middle Ages—so the story goes—local vile tyrant Marquis Raineri di Biandrate visited a young woman named Violetta on the eve of her wedding, intending to cash in his droit du seigneur.
But Violetta fought back, producing a dagger and lopping off the tyrant's head. When the villagers saw her holding the head aloft toward them in triumph, they took the opportunity to unleash the anger wrought from years of oppression. They stormed the castle, burned it to the ground, and vowed to never submit to tyranny again.
A few centuries pass, yadda yadda yadda, and the throwing of oranges to simulate the defeat of the tyrant becomes a yearly tradition, complete with rules for participants and guidelines for spectators. (Don't throw an orange at a horse; wear a red floppy cap if you don't want to get hit; no strollers.)
The next Battle of the Oranges takes place on the three days preceding Mardi Gras (February 15-17) in Ivrea, just north of Turin.