The situation was suddenly changed, however, and Philip was tardily forced again into the opposition against the Emperor, by the Treaty of Crépy of 1544, which opened his eyes to the danger threatening Protestantism. He prevented the Roman Catholic Duke Henry V of Brunswick-Lüneburg from taking forcible possession of his dominions and unsuccessfully planned a new alliance with German princes against Austria, pledging its members to prevent the acceptance of the decrees of the projected Council of Trent. When this failed, he sought to secure the neutrality of Bavaria in a possible war against the Protestants and proposed a new Protestant alliance to take the place of the Schmalkaldic League.