While all this was going on the Prince of Orange had been pushing forward the siege operations.  On July 17 the forts of St Isabella and St Anthony were stormed.  The attack against the main defences, in which the English regiments specially distinguished themselves, was now pressed with redoubled vigour.  The resistance at every step was desperate, but at last the moat was crossed and a lodgment effected within the walls.  On September 14 Hertogenbosch surrendered; and the virgin fortress henceforth became the bulwark of the United Provinces against Spanish attack on this side.  The consummate engineering skill, with which the investment had been carried out, attracted the attention of all Europe to this famous siege.  It was a signal triumph and added greatly to the stadholder’s popularity and influence in the republic.

It was needed.  The Estates of Holland were at this time once more refractory.  The interests of this great commercial and maritime province differed from those of the other provinces of the Union; and it bore a financial burden greater than that of all the others put together.  The Estates, then under the leadership of Adrian Pauw, the influential pensionary of Amsterdam, declined to raise the quota of taxation assigned to the province for military needs and proceeded to disband a number of troops that were in their pay.  Inconsistently with this action they declined to consider certain proposals for peace put forward by the Infanta Isabel, for they would yield nothing on the questions of liberty of worship or of freedom to trade in the Indies.  Their neglect to furnish the requisite supplies for the war, however, prevented the prince from undertaking any serious military operations in 1630.  Fortunately the other side were in no better case financially, while the death of Spinola and the withdrawal of the Count de Berg from the Spanish service deprived them of their only two competent generals.  This attitude of Holland, though it thwarted the stadholder’s plans and was maintained in opposition to his wishes, by no means however implied any distrust of him or lack of confidence in his leadership.  This was conclusively proved by the passing, at the instigation of Holland, of the Acte de Survivance (April 19,1631).  This Act declared all the various offices held by the prince hereditary in the person of his five-year-old son.  He thus became, in all but name, a constitutional sovereign.

An expedition planned for the capture of Dunkirk at this time, spring 1631, proved too hazardous and was abandoned, but later in the year the Dutch sailors gave a signal proof of their superiority at sea.  Encouraged by the failure of the attempted attack on Dunkirk the government at Brussels determined on a counter-stroke.  A flotilla of 35 frigates, accompanied by a large number of smaller vessels to carry supplies and munitions and having on board a body of 6000 soldiers, set sail from Antwerp under the command of Count John