Indignant at such concessions the Catholic party formed the League[9] with the young Duke of Guise at its head. Henry III., finding that it was impossible to oppose this combination with any hope of success, determined to control it by becoming himself its leader. The concessions made to the Huguenots were recalled (1577), and the fifth civil war broke out. This was brought to an end by the Peace of Poitiers (1577). The Huguenot party, under the King of Navarre and the young Prince de Conde, continued to make headway against the League, and sought to strengthen themselves by an alliance with England and the Netherlands. The question of the succession to the French throne became serious for both parties. Henry III. was childless, and on the death of the heir- apparent, his brother the Duke of Anjou (Alencon, 1584), the succession devolved apparently on Henry King of Navarre, but as he was a Calvinist the Catholics were unwilling to recognise him. The League declared Cardinal de Bourbon son of the Duke of Vendome as the lawful heir to the French throne, though many of its out and out supporters were in favour of the Duke of Guise. An attempt was made to get the approval of the Pope for the League and its policy, but both George XIII. and Sixtus V. were not inclined to support its pretensions. At the earnest request of Spain the latter, however, issued a constitution in 1585, by which he declared that Henry of Navarre and the Prince de Conde, as notorious heretics excommunicated by the Church, had forfeited all claim to the throne of France. Henry of Navarre lodged a solemn protest in Rome, and he appealed to the Parliament of Paris, which refused to approve of the publication of the papal document. Both sides had recourse once more to arms, and the Huguenots under the leadership of Henry of Navarre were victorious in the battle of Coutras (1587). The League however continued the struggle, captured some of the principal cities such as Lyons, Orleans, and Bourges, while Henry III. favoured both parties in turn. Overawed by the successful exploits of the Duke of Guise he pledged himself to put down the Huguenots, and the French people were called upon by royal proclamation to swear that they would never accept a heretic as their king (1588).