Sometimes I feel like complaining about how modern technology and social media cause people to blow small things way out of proportion, but then I remember that in 1325, the Italian city-states of Modena and Bologna went to war over this actual bucket and 2,000 people died pic.twitter.com/MesKN7DJjN— Katie Henry (@KT_NRE) September 7, 2018
It was provoked when Modenese soldiers stole the bucket from a city well, but was really an episode in the over 300-year-long struggle between Guelphs and Ghibellines. Modena won the Battle of Zappolino (the only battle of the war), and the bucket remains in Modena to this day.
From the late Middle Ages until the Renaissance, northern Italy was divided between factions supporting the rival political claims of the Holy Roman Emperor ("Ghibellines") and the Pope ("Guelfs"). Modena was Ghibelline; Bologna was Guelph.
In this atmosphere of tension and hostility, some Modenese soldiers slipped into the center of Bologna, and stole a civic bucket filled with loot from the main city well in the center of Bologna. The humiliated Bolognese demanded the return of the bucket, and when that was refused declared war on Modena.