Which pope excommunicated the crusaders after they attacked Zara in 1202?

Pope Innocent III excommunicated the crusaders after they attacked Zara in 1202.

Zara—now Zadar, Croatia—was a Catholic city under the protection of the king of Hungary, who had himself taken the cross. The Fourth Crusade reached the Adriatic after agreeing to pay Venice for ships and transport, but the crusaders could not meet the enormous bill. Venice proposed capturing Zara as compensation, despite the city’s Christian status.

Innocent III had forbidden the attack and warned the crusaders that participation would bring excommunication. Zara fell on 24 November 1202, and the city was pillaged. After learning what had happened, Innocent excommunicated the crusading army and the Venetians. The episode was a major turning point: the crusade had begun by attacking fellow Catholics rather than Muslims.

A common mix-up is to treat the excommunication as permanent for every participant. In February 1203, Innocent rescinded it for non-Venetian crusaders, whom he regarded as having been pressured or misled. He did not simply approve the assault; his letters had explicitly opposed it.