Upon the death of Frederick Henry of Orange (March, 1647), his only son succeeded to his titles and estates and also by virtue of the Act of Survivance to the offices of Stadholder in six provinces and to the Captain-Generalship and Admiral-Generalship of the Union.  William was but twenty-one years of age and, having been excluded during Frederick Henry’s lifetime from taking any active part in affairs of state, he had turned his energies into the pursuit of pleasure, and had been leading a gay and dissolute life.  His accession to power was, however, speedily to prove that he was possessed of great abilities, a masterful will and a keen and eager ambition.  He had strongly disapproved of the trend of the peace negotiations at Muenster, and would have preferred with the help of the French to have attempted to drive the Spaniards out of the southern Netherlands.  The preliminaries were, however, already settled in the spring of 1647; and the determination of the province of Holland and especially of the town of Amsterdam to conclude an advantageous peace with Spain and to throw over France rendered the opposition of the young Stadholder unavailing.  But William, though he had perforce to acquiesce in the treaty of Muenster, was nevertheless resolved at the earliest opportunity to undo it.  Thus from the outset he found himself in a pronounced antagonism with the province of Holland, which could only issue in a struggle for supremacy similar to that with which his uncle Maurice was confronted in the years that followed the truce of 1609, and, to a less degree, his father after 1640.

Commerce was the predominant interest of the burgher-aristocracies who held undisputed sway in the towns of Holland; and they, under the powerful leadership of Amsterdam, were anxious that the peace they had secured should not be disturbed.  They looked forward to lightening considerably the heavy load of taxation which burdened them, by reducing the number of troops and of ships of war maintained by the States.  To this policy the young prince was resolutely opposed, and he had on his side the prestige of his name and a vast body of popular support even in Holland itself, among that great majority of the inhabitants, both of town and country, who were excluded from all share in government and administration and were generally Orangist in sympathy.  He had also with him the officers of the army and navy and the preachers.  His chief advisers were his cousin William Frederick, Stadholder of Friesland, and Cornelis van Aerssens (son of Francis) lord of Sommelsdijk.  By the agency of Sommelsdijk he put himself in secret communication with Count d’Estrades, formerly French ambassador at the Hague, now Governor of Dunkirk, and through him with Mazarin, with the view of concluding an alliance with France for the conquest of the Spanish Netherlands, and for sending a joint expedition to England to overthrow the Parliamentary forces and establish the Stewarts on the throne.  Mazarin was at this time, however,