After the death of the Borgia pope Alexander VI and his short-lived Sienese successor Pius III Piccolomini, he helped Pope Julius II in the expenses attendant upon his election. The latter rewarded him, linking Chigi to the della Rovere family, and creating him treasurer and notary of the Apostolic Camera. The personal bond between the Pope and his banker remained close: Agostino accompanied Julius in the field in both his great military campaigns of 1506 and 1510. In 1511 Agostino was sent to Venice to buy Venetian support for the papal forces in the War of the League of Cambrai.