After the defeat at Marignano, the League no longer possessed the ability or the will to continue the war. Francis advanced on Milan, capturing the city on 4 October and removing Sforza from the throne. In December, he met with Leo at Bologna; the pope, who had in the meantime been deserted by the remainder of his Swiss mercenaries, surrendered Parma and Piacenza to Francis and Modena to the Duke of Ferrara. In return, Leo received guarantees of French noninterference in his proposed attack on the Duchy of Urbino. Finally, the Treaty of Noyon, signed by Francis and Charles V in August 1516, recognized French claims to Milan and Spanish claims to Naples, removing Spain from the war. Maximilian held out, making another attempt to invade Lombardy; his army failed to reach Milan before turning back, and by December 1516, he had entered into negotiations with Francis. The resulting Treaty of Brussels not only accepted French occupation of Milan, but also confirmed Venetian claims to the remainder of the Imperial possessions in Lombardy , effectively ending the war with a return to the status quo of 1508. The peace, however, would last only four years; the election of Charles V as Holy Roman Emperor in 1519 caused Francis, who had desired the position for himself, to begin the Italian War of 1521-26. The Italian Wars, thus reignited, would then continue until 1530 without significant interruption.
Question: Who deserted the Pope?
Answer: his Swiss mercenaries