The coast of the Baltic, on the other hand, possesses few islands, the chief being Alsen and Fehmarn off the coast of Schleswig-Holstein, and Rtigen off Pomerania.
A defensive alliance with Sobieski (August 4, 1677) was rendered inoperative by the annihilation of Sweden's sea-power (battle of Oland, June 17, 1676; battle of Fehmarn, June 1677) and the difficulties of the Polish king.
The islands of Alsen and Fehmarn are separated from the coast by narrow channels.
But the Swedish fleet escaped, and the annihilation of the Danish fleet by the combined navies of Sweden and Holland, after an obstinate fight between Fehmarn and Laaland at the end of September, exhausted the military resources of Denmark and compelled Christian to accept the mediation of France and the United Provinces; and peace was finally signed at BrOmsebro on the 8th of February 1645.