IV of France touching the conditions on which he would accept the sovereignty of the Provinces.  Indeed it is said that such was the despair felt by this great statesman, who knew better than any man the economic difficulties of the situation, that he even contemplated the possibility of submission to the archdukes.  Had he suggested submission, there would have been no question, however, that he could not have retained office, for Maurice, William Lewis and the military leaders on the one hand, and on the other the merchants and the adventurous seamen, whom they employed in the profitable Indian traffic, would not have listened for a moment to any thought of giving up a struggle which had been so resolutely and successfully maintained for so many years.  For financially the archdukes were in even worse plight than the Netherlanders, even though for a short time, with the help of Spinola, appearances seemed to favour the Belgic attacks on the Dutch frontier districts.  In 1605 the Genoese general, at the head of a mixed but well-disciplined force in his own pay, made a rapid advance towards Friesland, and, after capturing Oldenzaal and Lingen and ravaging the eastern provinces, concluded the campaign with a brilliant success against a body of the States cavalry commanded by Frederick Henry, who nearly lost his life.  Maurice with inferior forces kept strictly on the defensive, skilfully covering the heart of the land from attack, but steadily refusing a pitched battle.  In the following year Spinola with two armies attempted to force the lines of the Waal and the Yssel, but, though thwarted in this aim by the wariness of the stadholder and by a very wet season, he succeeded in taking the important fortresses of Groll and Rheinberg.  Maurice made no serious effort to relieve them, and his inactivity caused much discontent and adverse comment.  His military reputation suffered, while that of his opponent was enhanced.  But subsequent events showed that Maurice, though perhaps erring on the side of caution, had acted rightly.  The armies which had threatened the safety of the Provinces had been raised at the charges of a private individual, but the financial resources, even of a Spinola, were not capable of a prolonged effort; there was no money in the State treasury; and the soldiery, as soon as their pay was in arrears, began once more to be mutinous.  The bolt had been shot without effect, and the year 1607 found both sides, through sheer lack of funds, unable to enter upon a fresh campaign on land with any hope of definite success.  But though the military campaigns had been so inconclusive, it had been far different with the fortunes of maritime warfare in these opening years of the seventeenth century.  The sea-power of the Dutch republic was already a formidable factor which had to be reckoned with and which was destined to be decisive.