During the six terrible years of Alva's rule in the Netherlands (1567-1573) the Dutch sea forces contributed heavily toward the maintenance of the war, assured control of the Holland and Zealand coasts, and more than once, as at Brill and Leyden, proved the salvation of the patriot cause. Holland and Zealand, the storm-centers of rebellion, were not again so devastated, though the war dragged on for many years, maintained by the indomitable spirit of William of Orange until his assassination in 1584, and afterward by the military skill of Maurice of Nassau and the aid of foreign powers. The seven provinces north of the Scheldt, separating from the Catholic states of the south, prospered in trade and industry as they shook themselves free from the stifling rule of Spain. By a twelve-year truce, finally ratified in 1609, they became "free states over which Spain makes no pretensions," though their independence was not fully recognized until the Peace of Westphalia in 1648. The war, while it ruined Antwerp, increased the prosperity of Holland and Zealand, which for at least twenty years before the truce were busily extending their trade to every part of the world. _Growth of Dutch Commerce_ The story of this expansion of commerce is a striking record. The grain and timber of the Baltic, the wines of France and Spain, the salt of the Cape Verde Islands, the costly wares of the east, came to the ports of the Meuse and Zuyder Zee. In 1590 the first Dutch traders entered the Mediterranean, securing, eight years later, the permission of the Sultan to engage in Constantinople trade. In 1594 their ships reached the Gold Coast, and a year later four vessels visited Madagascar, Goa, Java, and the Moluccas or Spice Islands. A rich Zealand merchant had a factory at Archangel and a regular trade into the White Sea. Seeking a reward of 25,000 florins offered by the States for the discovery of a northeast passage, Jacob van Heimskirck sailed into the Arctic and wintered in Nova Zembla; Henry Hudson, in quest of a route northwestward, explored the river and the bay that bear his name and died in the Polar Seas. Statistics, while not very trustworthy and not enlightening unless compared with those for other nations, may give some idea of the preponderance of Dutch shipping. At the time of the truce she is said to have had 16,300 ships, about 10,000 of which were small vessels in the coasting trade. Of the larger, 3000 were in the Baltic trade, 2000 in the Spanish, 600 sailed to Italy, and the remainder to the Mediterranean, South America, the Far East, and Archangel. The significance of these figures may be made clearer by citing Colbert's estimate that at a later period (1664) there were 20,000 ships in general European carrying trade, 16,000 of which were Dutch. Throughout the 17th century Dutch commerce continued to prosper, and did not reach its zenith until early in the century following.