Frederick Henry was at this period in his forty-second year. His military reputation was well established; he soon proved his political talents. He commenced his career by a total change in the tone of government on the subject of sectarian differences. He exercised several acts of clemency in favor of the imprisoned and exiled Arminians, at the same time that he upheld the dominant religion. By these measures he conciliated all parties; and by degrees the fierce spirit of intolerance became subdued. The foreign relations of the United Provinces now presented the anomalous policy of a fleet furnished by the French king, manned by rigid Calvinists, and commanded by a grandson of Admiral Coligny, for the purpose of combating the remainder of the French Huguenots, whom they considered as brothers in religion, though political foes; and during the joint expedition which was undertaken by the allied French and Dutch troops against Rochelle, the stronghold of Protestantism, the preachers of Holland put up prayers for the protection of those whom their army was marching to destroy. The states-general, ashamed of this unpopular union, recalled their fleet, after some severe fighting with that of the Huguenots. Cardinal Richelieu and the king of France were for a time furious in their displeasure; but interests of state overpowered individual resentments, and no rupture took place. Charles I. had now succeeded his father on the English throne. He renewed the treaty with the republic, which furnished him with twenty ships to assist his own formidable fleet in his war against Spain. Frederick Henry had, soon after his succession to the chief command, commenced an active course of martial operations, and was successful in almost all his enterprises. He took Groll and several other towns; and it was hoped that his successes would have been pushed forward upon a wider field of action against the imperial arms; but the States prudently resolved to act on the defensive by land, choosing the sea for the theatre of their more active operations. All the hopes of a powerful confederation against the emperor and the king of Spain seemed frustrated by the war which now broke out between France and England. The states-general contrived by great prudence to maintain a strict neutrality in this quarrel. They even succeeded in mediating a peace between the rival powers, which was concluded the following year; and in the meantime they obtained a more astonishing and important series of triumphs against the Spanish fleets than had yet been witnessed in naval conflicts.