After decades of tension, war broke out between Protestants and Catholics after the massacre of Vassy in 1562. In 1572, after several unsuccessful peace attempts, Charles ordered the marriage of his sister Margaret of Valois to Henry of Navarre (the future King Henry IV of France), a major Protestant nobleman in the line of succession to the French throne, in a last desperate bid to reconcile his people. Facing popular hostility against this policy of appeasement, Charles allowed the massacre of all Huguenot leaders who gathered in Paris for the royal wedding at the instigation of his mother Catherine de' Medici. This event, the St. Bartholomew's Day massacre, was a significant blow to the Huguenot movement, though religious civil warfare soon began anew. Charles sought to take advantage of the disarray of the Huguenots by ordering the Siege of La Rochelle, but was unable to take the Protestant stronghold.