In the war with Denmark which broke out in 1643 the narrow but unflinching patriotism of Oxenstjerna showed itself to better advantage. [Sidenote: =War with Denmark, 1643.=] Free passage through the Sound and the Belts for Swedish ships was as much a commercial necessity for the development of Swedish trade, as free passage through the passes of Savoy was a military necessity for the aggrandisement of France. But Denmark seated astride of the islands, with one foot on Halland and the other on Jutland, by merely raising the dues payable for the passage of ships, could crush the nascent trade at its birth. In doing so it had to reckon not merely with Sweden but with the more important maritime countries of Holland and England who carried on with Sweden, through the Sound, a prosperous and growing trade in skins, fur and copper, and were therefore keenly interested in the question of the Sound tolls. But in 1639, seeing England involved in domestic trouble, and Holland fully occupied in the ceaseless struggle with Spain, Christian IV. thought the opportunity had come for vigorous action. He raised the tolls on the Sound, attempted to take the lead in German affairs by putting himself forward as mediator in the negotiations for peace, and in July 1640 directly insulted the government of Sweden by openly assisting the queen-mother, Maria Eleonora of Brandenburg to escape from the dignified seclusion in which she was kept. For the moment Oxenstjerna had to temporise, for the affairs of Germany absorbed his whole energies, but two years later the opportunity came. Torstenson was suddenly directed upon Holstein without any declaration of war, and in conjunction with Horn quickly overran the whole of the mainland. Christian taken by surprise had to betake himself to his islands and his ships. There he fought like a hero, holding his own manfully for two summers against the combined efforts of Swedish fleets and Dutch sailors. [Sidenote: =The treaty of Brömsebro, 1645.=] But the odds were too many for him, and after a severe defeat in October 1644 he found himself obliged to sue for peace. The next year, in August 1645, the treaty of Brömsebro was negotiated through the mediation of France between Christian and Oxenstjerna. [Sidenote: =Acquisition of Halland and freedom from the Sound dues.=] By it Sweden was entirely relieved from the payments of tolls on the Sound and the Belts, and acquired the province of Halland on terms which practically involved its annexation. However questionable on the score of public faith its beginning may have been, there is no doubt that this was one of the most important and useful wars waged by Sweden in the seventeenth century. At very little expense to herself, she completed the work of national consolidation by making Denmark retire across the natural frontier of the sea, and secured for the future the free and unhampered development of her commerce. Both