Although not formally part of the 1635 to 1659 Franco-Spanish War, Savoy's strategic importance drew in both Habsburg Spain, which controlled the nearby Duchy of Milan, and France.

Following the death of Victor Amadeus I, Duke of Savoy in October 1637, his wife Christine of France was appointed Regent for their young son, Francis Hyacinth.

French control of Piedmont prevented foreign powers gaining access to the restive southern provinces of the Dauphiné and Vaunage, former Huguenot strongholds with a long history of rebellion.

That ended with their candidate, Charles I Gonzaga, confirmed as ruler of the Duchy of Mantua, and French garrisons were installed in the Savoyard fortresses of Pinerolo and Casale.

[2] Like many rulers, Victor Amadeus tried to balance both sides; his younger brother, Thomas Francis, Prince of Carignano, was a military leader of considerable ability, who commanded Spanish troops against France at Les Avins in May 1635.

[4] In June 1637, Leganés, Spanish governor of Milan, captured the Savoyard town of Vercelli; the anti-Habsburg alliance in Northern Italy fell apart when Charles of Mantua died in September, followed by Victor Amadeus in October.

[7] The Princes, or 'Principisti', had considerable support among ordinary Piedmontese, who resented the French presence; those who backed Christine, known as 'Madamisti', included a number of powerful families, notably the d'Aglié clan.

In March 1639, Thomas entered Piedmont, quickly occupying Chieri, Moncalieri, Ivrea, Verrua and Chivasso, but the main prize was Turin, held by a French garrison.

[11] In June, Christine ceded Cherasco and Carmagnola to France, in return for an annual subsidy of one million Écus; she also agreed to 'discuss' the future of Savoyard possessions including the County of Nice.

However, Leganés advanced on Chieri from the south, and Thomas marched out of Turin; threatened with from two sides, Harcourt withdrew towards Pinerolo on 20 November, only to find his road blocked by the Spanish.

Leganés had been replaced as Habsburg commander by Cardinal Trivulzio, who tried to support Thomas as best he could, but in 1640, protests against tax increases erupted into open revolts in Portugal and Catalonia.

[18] When Thomas' brother-in-law, the Comte de Soissons, was killed at La Marfée in July 1641, it left his sister Marie as heir and gave Richelieu a powerful bargaining tool.

In return, Thomas received a pension, his wife's inheritance, and help in securing the release of his family from Spain; Maurice was granted the governorship of Nice, and renounced his position as cardinal to marry his niece, Princess Luisa Cristina of Savoy.

[20] Although the civil war was ended, the final settlement has been seen as benefitting France, which retained garrisons in Turin, Pinerolo and Casale, while neutralising any opposition to French control.