In March 1629, the French stormed Savoyard positions in the Pas de Suse, lifted the Spanish siege of Casale and captured Pinerolo. The Treaty of Suza then ceded the two fortresses to France and allowed their troops unrestricted passage through Savoyard territory, giving them control over Piedmont and the Alpine passes into southern France. However, as soon as the main French army withdrew in late 1629, the Spanish and Savoyards besieged Casale once again. At the same time, the Spanish employed mercenaries paid for by Ferdinand II in an offensive which routed the main Venetian field army and forced Nevers to abandon Mantua. By October 1630, the French position seemed so precarious their representatives agreed the Treaty of Ratisbon, but it was never ratified as Richelieu claimed he had never approved the terms.
In March 1629, the French stormed Savoyard positions in the Pas de Suse, lifted the Spanish siege of Casale and captured Pinerolo. The Treaty of Suza then ceded the two fortresses to France and allowed their troops unrestricted passage through Savoyard territory, giving them control over Piedmont and the Alpine passes into southern France. However, as soon as the main French army withdrew in late 1629, the Spanish and Savoyards besieged Casale once again At the same time, the Spanish employed mercenaries paid for by Ferdinand II in an offensive which routed the main Venetian field army and forced Nevers to abandon Mantua. By October 1630, the French position seemed so precarious their representatives agreed the Treaty of Ratisbon, but it was never ratified as Richelieu claimed he had never approved the terms.