ITALY /ITALIAN STATES  MANTUA   CARLO GONZAGA 1629  4 SOLDI VERY RARE

The War of the Mantuan Succession (1628–1631) was a related conflict of the Thirty Years' War, caused by the death in December 1627 of Vincenzo II, last male heir in the direct line of the House of Gonzaga and ruler of the duchies of Mantua and Montferrat. The territories were key to control of the Spanish Road, an overland route that allowed Habsburg Spain to move recruits and supplies from their Italian possessions to their army in Flanders. The result was a proxy war between France, who supported the French-born Duke of Nevers, and Spain, who backed his distant cousin the Duke of Guastalla.

Fighting centred on the fortress of Casale in Montferrat, which the Spanish besieged twice, from March 1628 to April 1629, then September 1629 to October 1630. French intervention on behalf of Nevers in April 1629 led to the transfer of Imperial troops from Northern Germany to support Spain. Despite taking Mantua in July 1630, the French-backed Swedish intervention in the Thirty Years' War forced Emperor Ferdinand II to withdraw his troops and make peace.

The June 1631 Treaty of Cherasco confirmed Nevers as Duke of Mantua and Montferrat, in return for minor territorial losses. More importantly, it left the French in possession of Pinerolo and Casale, which controlled access to passes through the Alps. The diversion of Imperial and Spanish resources from Germany allowed the Swedes to establish themselves within the Holy Roman Empire and was a key reason the Thirty Years War continued until 1648