This expedition under Marten Thijssen, who after his victory was created a Swedish noble and definitely entered the Swedish naval service, though connived at by Frederick Henry and the States-General, did not express any desire on their part to aggrandise Sweden unduly at the expense of Denmark.  If some great merchants such as Louis de Geer and Elias Trip were exploiting the resources of Sweden, others, notably a certain Gabriel Marcelis, had invested their capital in developing the Danish grazing lands; and politically and commercially the question of the Sound dues, pre-eminently a Danish question, overshadowed all others in importance.  The Dutch had no desire to give Sweden a share in the control of the Sound; they preferred in the interests of their vast Baltic trade to have to deal with Christian IV alone.  The Swedish threat was useful in bringing diplomatic pressure to bear on the Danish king, but ultimately they felt confident that, if he refused to make concessions in the matter of the dues, they could compel him to do so.  As one of their diplomatists proudly declared, “the wooden keys of the Sound were not in the hands of King Christian, but in the wharves of Amsterdam.”  In June, 1645, his words were put to a practical test.  Admiral Witte de With at the head of a fleet of fifty war-ships was ordered to convoy 300 merchantmen through the Sound, peacefully if possible, if not, by force.  Quietly the entire fleet of 350 vessels sailed through the narrow waters.  The Danish fleet and Danish forts made no attempt at resistance.  All the summer De With cruised to and fro and the Dutch traders suffered no molestation.  Christian’s obstinacy at last gave way before this display of superior might, and on August 23, by the treaty of Christianopel he agreed to lower the tolls for forty years and to make many other concessions that were required from him.  At the same time by Dutch mediation peace was concluded between Denmark and Sweden, distinctly to the advantage of the former, by the treaty of Broemsebro.

To pass to other regions.  In the Levant, during the long residence of Cornelis Haga at Constantinople, trade had been greatly extended.  Considerable privileges were conceded to the Dutch by the so-called “capitulation” concluded by his agency with the Porte in 1612; and Dutch consuls were placed in the chief ports of Turkey, Asia Minor, Syria, Egypt, Tunis, Greece and Italy.  The trading however with the Mediterranean and the Levant was left to private enterprise, the States-General which had given charters to the different Companies—­East India, West India and Northern—­not being willing to create any further monopolies.

The lack of coal and of metals has always seriously hindered industrial development in the United Provinces.  Nevertheless the advent into Holland of so many refugees who were skilled artisans, from the southern Netherlands, led to the establishment of various textile industries at Leyden, Haarlem and other towns.  One of the chief of these was the dressing and dyeing of English cloth for exportation.