When cardinals couldn't elect a Pope after two years of deadlock, the townspeople locked them in, cut their food to bread and water, and started removing the roof. It worked.
Pope Clement IV died in November 1268, leaving behind a College of Cardinals so bitterly divided between French Angevin and Italian factions that they couldn't agree on a successor. The deadlock dragged on for months, then years — eventually becoming the longest papal vacancy in the history of the Catholic Church.
The cardinals met in Viterbo, Italy, in the Palace of the Popes. By 1270, after nearly two years of fruitless voting, the citizens of Viterbo had lost patience. The local magistrates literally locked the cardinals inside the palace and posted guards to prevent them from leaving.
When locking them in still produced no result, the townspeople escalated. They reduced the cardinals' rations to bread, water, and a small amount of wine. When that also failed, they began physically dismantling the roof of the palace above the cardinals' heads — exposing them to the Italian summer heat and the elements.
Three cardinals died during the three-year conclave, and one resigned, leaving only 16 to vote. With the process completely broken, the survivors agreed on a novel solution: they delegated the entire decision to a committee of just six cardinals, who chose Teobaldo Visconti — a man who wasn't even a priest and was away on Crusade at the time.
The new pope, Gregory X, drew a direct lesson from his own chaotic election. In 1274, he issued a formal decree — Ubi periculum — establishing binding rules for papal conclaves. He essentially codified exactly the coercive tactics used against him in Viterbo: sequestration, reduced rations, and physical exposure if cardinals failed to reach agreement promptly.
The word 'conclave' comes from the Latin con clave, meaning 'with a key' — a direct reference to the locked rooms of Viterbo. The election of 1268 essentially invented the modern process for choosing a pope, born directly out of one of the most dysfunctional elections in church history.