for the Grand Duke of Tuscany) would be appropriate. Francesco Barberini refused. The Duke took his leave but urged the Pope to chastise both Cardinal-nephews. The nephews were furious and convinced the pope to punish the Duke by banning grain shipments originating in Castro from being distributed in Rome and the surrounding territory, thereby depriving the Duke of an important source of income. Duke Odoardo's Roman creditors saw their chance - the Duke was unable to pay his debts, which he had accumulated in military adventures against the Spanish in Milan and in luxurious living. The unpaid and unhappy creditors sought relief from the pope, who turned to military action in an attempt to force payment. Preparations for war Pope Urban VIII responded to the requests of Duke Odoardo's creditors by sending his nephew Antonio, Fabrizio Savelli and Marquis Luigi Mattei to occupy the city of Castro. Papal forces also included commanders Achille d'Étampes de Valençay and Marquis Cornelio Malvasia. At the same time, the pope sent cardinal Bernardino Spada as plenipotentiary in an effort to resolve the crisis. Spada successfully negotiated a truce but when the pope's military leaders became aware that the dukes were massing troops to counter their own (in case discussions with Spada came to naught), Urban VIII declared the articles of peace null and void and claimed Spada had negotiated them without his consent. Spada later published a manifesto detailing his version of events which, according to contemporary John Bargrave, many accepted to be the truth. Urban VIII had been amassing troops in Rome throughout 1641. Mercenaries and regular troops filled the streets and Antonio Barberini was forced to institute special measures to maintain authority over the city. But the papacy needed yet more troops. The Duke of Ceri, who had been imprisoned for wounding a papal officer in a dispute over the management of the Duchy of Ceri, and Mario Frangipani, imprisoned for murdering someone on his estate, were both pardoned by the pope and given command of papal troops. First War of Castro On 12 October, Luigi Mattei led 12,000 infantry and up to 4,000 cavalry against the fortified town. The pope's forces were met by a contingent of 40 troops guarding a bridge leading to the town; a short burst of cannon-fire resulting in a single death was enough to prompt capitulation. Castro, and several other small towns nearby, surrendered. Fabrizio Savelli,