This double disaster destroyed the Pope's plans for the crusade, as he had envisaged it to land in Theodore's rear while he was engaged with Robert's army. At the same time, the prospective leader of the crusade, William VI of Montferrat, fell ill. In November, the Pope was forced to postpone the crusade's departure for the next spring. With news of the Latin defeats and the postponement of the crusade, the exhausted defenders of Thessalonica surrendered the city to Theodore sometime in December 1224. The crusade to relieve it sailed in March 1225, and landed in Thessaly at Halmyros. The Crusader army was soon decimated by dysentery, allegedly because the Greeks had poisoned the local water supply. William of Montferrat himself succumbed to it, and the remnants of the army left Greece. Demetrius of Montferrat still hoped to recover his realm with the help of Frederick II, but died in 1227.