Although in previous reigns, younger sons of Savoy had been granted rich appanages in Switzerland (Genevois, Vaud), Italy (Aosta), or France (Nemours, Bresse), the Savoy dukes found that this inhibited their own aggrandizement while encouraging intra-dynastic strife and regional secession. Not only did Thomas Francis have older brothers, but he was just one of the twenty-one acknowledged children of Charles Emmanuel. While only nine of these were legitimate, the others, being the widowed duke's offspring by noble mistresses, appear to have been generously endowed or dowered during their father's lifetime.[2]
The fief of Carignano had belonged to the Savoys since 1418, and the fact that it was part of Piedmont, only twenty kilometers south of Turin, meant that it could be a "princedom" for Thomas in name only, being endowed neither with independence nor revenues of substance.[3] Instead of receiving a significant patrimony, Thomas was wed in 1625 to Marie de Bourbon, sister and co-heiress of Louis, Count of Soissons, who would be killed in 1641 while fomenting rebellion against Cardinal Richelieu.
In anticipation of this inheritance, Thomas Francis and Marie did not establish themselves at his brother's ducal capital, Turin, but dwelt in Paris, where Marie enjoyed the exalted rank of a princesse du sang, being a second cousin of King Louis XIII. It was arranged that Thomas Francis, as son of a reigning monarch, would hold the rank of first among the princes étrangers at the French court —- taking precedence even before the formerly all-powerful House of Guise, whose kinship to the sovereign Duke of Lorraine was more remote.[1] He was appointed Grand Maître of the king's household, briefly replacing the traitorous Grand Condé. He engaged the services of the distinguished grammarian and courtier Claude Favre de Vaugelas as tutor for his children.
The prospect of Marie's eventual succession to the Swiss principality of Neuchâtel, near Savoy, was foiled in 1643 by the king's decision to legitimate Louis Henri de Bourbon, chevalier de Soissons (1640–1703), a son of Marie's late brother. This prevented the substitution of Savoyard for French influence in that region, but left Thomas with little more than the empty title of "prince de Carignan". Marie did eventually inherit her brother's main holding in France, the county of Soissons, but this would be established as a secundogeniture for the French branch of the family. After Thomas Francis, the senior branch of his descendants repatriated to Savoy, alternately marrying French, Italian and German princesses.[2]
The first recorded military service of Thomas Francis is as a commander in the Savoyard army under his father against France during the War of the Mantuan Succession in 1630. Cardinal Mazarin induced him to become, in effect, a French agent at the Savoyard court between 1630 and 1632. When the new Duke Victor Amadeus I was forced to accept French occupation of Pinerolo in the Peace of Cherasco in 1631, there was widespread dissatisfaction in Savoy, and Thomas Francis, with his brother, Prince Maurice, withdrew from the duchy to join the forces of Spain, prompting Victor Amadeus to confiscate his uncles' Italian revenues. Though his kinship to both the French and Spanish royal families suggested that he could be useful to Spanish interests, Thomas Francis was not entirely trusted, and was obliged to send his wife and children to Madrid as hostages.[4]
When France launched the Franco-Spanish War (1635–59), Thomas Francis served under the Cardinal-Infante Ferdinand, brother of Philip IV in the Spanish Netherlands. Savoy was reluctantly dragged into the fighting alongside the French, consequently Thomas Francis was, strictly, fighting against his own homeland. He was completely defeated and his army entirely killed, captured or scattered - the first in an unbroken career of military defeats. He managed to rally the remnants at Namur, then retreated before the numerically superior French and Dutch forces; and he probably served the rest of the campaign with Ferdinand.
In 1636, Thomas Francis served with the Cardinal-Infante Ferdinand who organised a joint Spanish-Imperialist army for a major invasion of France from the Spanish Netherlands. The invasion was initially very successful, and seemed capable of reaching Paris, where there was a great panic; if Ferdinand and Thomas had pushed on, they might have ended the war at this point, but they both felt that continuing to Paris was too risky, so they stopped the advance. Later in the campaign, Thomas had problems with the Imperialist general Ottavio Piccolomini, who refused to accept orders from the Prince as a Spanish commander, arguing that his Imperialist troops were an independent force.
In this year, when his brother-in-law Louis de Bourbon, comte de Soissons fled from France after his failed conspiracy against Cardinal Richelieu, Thomas Francis acted as intermediary between Soissons and the Spanish in negotiations which led to a formal alliance between the count and Philip IV of Spain concluded 28 June 1637 - although within a month Soissons had reconciled with France. In 1638, Thomas served in Spanish Flanders, helping to defend the fortress-city of Saint-Omer against a French siege.[5]
Arms of the Soissons branch of the House of Savoy-CarignanoPrince Eugène Maurice of Savoy (1633–1673), Count of Soissons and Dreux, married Olympia Mancini, most notorious of the Mazarinettes, intrigante of the affaire des poisons and exiled in succession from both France and Spain. He also the progenitor of the House of Savoy-Soissons. This couple's son, Prince Eugene of Savoy, spurned by France due to his mother's disgrace when he sought to take up his place there as a prince étranger and military captain, defected to the service of the Holy Roman Emperor, where his generalship afflicted France for decades.
Among the children of Prince Thomas Francis and Marie de Bourbon-Soissons were:
