In 1623 the Leagues entered into an alliance with France, Savoy and Venice. Jürg Jenatsch and Ulysses von Salis used French money to hire an 8,000-man mercenary army and drive out the Austrians. The peace treaty of Monzon (5 March 1626) between France and Spain, confirmed the political and religious independence of the Valtellina. In 1627 the French withdrew from the Valtellina valley, which was then occupied by Papal troops. Starting in 1631 the League, under the French Duke Henri de Rohan, started to expel the Spaniards. However, Richelieu still did not want to hand the valley over to its residents. When it became clear that the French intended to remain permanently in the Leagues, but would not force the Valtellina to convert to Protestantism, Jürg Jenatsch (now a mercenary leader) converted in 1635 to the Catholic faith. In 1637, he rebelled and allied with Austria and Spain. His rebellion along with the rebellion of 31 other League officers forced the French to withdraw without a fight. On 24 January 1639, Jürg Jenatsch was killed during Carnival by an unknown attacker who was dressed as a bear. The attacker may have been a son of Pompeius Planta or an assassin hired by the local aristocracy. According to legend he was killed by the same axe that he used on Pompeius Planta. On 3 September 1639 the Leagues agreed with Spain to bring the Valtellina back under League sovereignty, but with the promise to respect the free exercise of the Catholic faith. Treaties with Austria in 1649 and 1652, brought the Müstair and Lower Engadine valleys back under the authority of the Three Leagues.