Richelieu sent Mazarin on several delicate diplomatic missions, including a long trip to Savoy to straighten out the tangled political affairs there: the regency of Christine, the Duchess of Savoy, and sister of Louis XIII, was challenged by her brothers-in-law, the princes Maurice and Thomas of Savoy. (See Piedmontese Civil War) Mazarin successfully secured Christine's position, and established a solid alliance between Savoy and France. This task kept him away from Paris for nine months, until June 1641. On 16 December 1641, though he had not reached his fortieth birthday, he received what he most desired, he was formally made a Cardinal.