Per Wikipedia

The Battle of the Oranges is a festival in the Northern Italian city of Ivrea, which includes a tradition of throwing of oranges between organized groups. It is the largest food fight in Italy and surrounding countries.

Every year the citizens remember their liberation with the Battle of the Oranges, where teams of aranceri (orange handlers) on foot throw oranges (representing old weapons and stones) against aranceri riding in carts (representing the tyrant’s ranks). During the 19th-century French occupation of Italy, the Carnival of Ivrea was modified to add representatives of the French army. Another adaptation of the story has the oranges used to symbolize the removed testicles of the tyrant.