In the summer of 1657, Denmark launched hostile actions against Sweden. Charles X, king of Sweden, who at the time was engaged in a war in Poland, marched his army at great speed to Jutland, the westernmost part of Denmark. The conquest of Jutland was completed in November 1657, but in the absence of an adequate naval force, Charles X could not carry his campaign to Zealand, the island on which Copenhagen is situated. Unexpectedly, the severe winter of 1657–58 came to his aid. In February 1658 the Little Belt (separating Jutland from the island of Fünen) as well as the Great Belt (separating Fünen from Zealand) froze over completely and, apparently, to a sufficient depth that the Swedish Army was able to cross over the frozen sea areas from Jutland to Zealand and force the Danes to sue for peace. Ice also played a major role in earlier Scandinavian history.
Some excerpts are cited from contemporary literature (and diaries) describing the harshness of the winter of 1657–58 in other European countries. Not only rivers, including major rivers, and lakes froze over but also the coastal waters of Flanders and the Netherlands as well as the Danish sea areas. An estimate of the air temperature of the winter of 1657–58 in the Netherlands is also given.
1 Part 1, “The Mongol Invasions of Japan,” was published in the November 1975 Bulletin (56, 1167–1171); Part 2, “The Year Leading to the Revolution of 1789 in France,” was published in the February 1977 Bulletin (58, 163–168).