The direct line of Mantua's Gonzaga family had come to an end in 1627 with the vicious and weak Vincenzo II, who on December 26 had died at the age of thirty-three on the same day that his niece Maria Gonzaga's marriage with Charles de Nevers was celebrated.
Nevers, the eldest son and heir of Charles, Duke of Nevers, Rethel and Mayenne, is the head of the cadet branch of the House of Gonzaga, and after Vincenzo II, heir of the Duchy of Mantua.
The Duke of Nevers is a son of Luigi, younger brother of Vincenzo II's grandfather.
Luigi had been naturalized French as Louis about 1550, and in 1566 had married the heiress of the duchies of Nevers and Rethel.
The French Crown would naturally prefer Nevers, a French peer, as ruler in Mantua.
Nevers arrives here in January of 1628 and proclaims himself its sovereign.
There are two rival claimants.
One is Charles Emmanuel I, Duke of Savoy, whose daughter Margerita is the widow of Francis IV.
Although their son had died an infant in 1612, it is their elder daughter Maria (1612-1660) who had married Charles de Nevers in 1627.
Charles Emmanuel bases his right to Mantua on his daughter's claim to a substantial portion of the Gonzaga realm, the Marquessate of Montferrat, which is demonstrably heritable by females since the Gonzagas had acquired it through marriage to Margherita Paleologa in 1540.
The other claimant is Ferrante II, Duke of Guastalla, a distant Gonzaga cousin who had voiced his claim but had not immediately placed troops in the field.
He is, however, supported by Emperor Ferdinand II, whose wife at the time, Eleanor of Mantua the elder (1598-1655), had been the sister of the last three Dukes of Mantua.
He seeks to reattach the Duchy of Mantua to the Holy Roman Empire; Ferrante, being in the Spanish-Imperial camp, is a useful tool to that purpose.
As the Thirty Years War wears on, it affects dynastic alliances.
Charles Emmanuel obtains support from the Habsburgs, who control Milan.
The resulting French-Habsburg war over the succession is just one of the many theaters of the Thirty Years War, fought all over Europe.
The initial attempt of Don Gonzalo Fernandez de Córdoba, Spanish governor of Milan, and Charles-Emmanuel is to partition the Mantuan-Montferrat patrimony, which lies to east and to west of Milan.
