Victor Amadeus became Duke after the death of his father on 26 July 1630. When Christine's husband died in 1637, she was created regent in the name of her son
Francis Hyacinth. At the death of Francis Hyacinth in 1638, her second son
Charles Emmanuel II succeeded and Christine retained the regency. Both
Prince Maurice and his younger brother
Prince Thomas of Savoy disputed the power of their sister-in-law and her French entourage. When the first heir
Francis Hyacinth died in 1638, both brothers started the
Piedmontese Civil War with Spanish support. The two parties were called "
principisti" (supporters of the Princes) and "
madamisti" (supporters of Madama Reale). After four years of fighting, Christine was victorious, thanks to French military support. Not only did she keep the Duchy for her son, she also prevented France getting too much power in the Duchy. When peace was concluded in 1642, Maurice married his fourteen-year-old niece Louise Christine, abandoning the title of cardinal and asking dispensation from
Pope Paul V. Maurice became governor of
Nice. Christine of France stayed in firm control of the Duchy of Savoy until her son could follow in her footsteps; her formal regency ended in 1648, but she remained in charge at his invitation until her death. She lived an uninhibited private life and had relationships with the French Ambassador, Marini, her brother-in-law, Maurice, and Count Filippo d'
Aglié. ==Later life==