After four years of fighting, Christine was victorious thanks to French military support of her brother Louis XIII. Not only did she keep the duchy for her son, she also prevented France getting too much power within her sons dominions thus preserving power for herself. When peace was concluded in 1642, Prince Maurice married Christines eldest daughter Luisa Cristina to cement the peace. Christine stayed in control of Savoy, until her son could follow in her footsteps. Even though her formal regency ended in 1648, she remained ruler of Savoy till her death. 