"I assure your Majesty that it was so cold," wrote the French ambassador to Louis XIV, "that one had to use an axe to cut the bread, as well as to break up beer and wine barrels. The King of Sweden merely laughed at such discomforts, although he shared them. His only thought was to succeed in his daring plan."
It was early 1658, and the Swedish King was Charles X, a brilliant general and not one to be trifled with. But the Danes, rather foolishly, had trifled. While Charles was at war in Poland, they attacked Sweden's possessions on the Baltic, and the northern monarch decided they must be taught a lesson. Marching from the south, he had little difficulty in gaining control of the Jutland peninsula - the "mainland" of Denmark - while the Danes hurriedly retreated to their capital at Copenhagen.
Now Denmark is a land of bits and pieces. Copenhagen lies on the large island of Zealand close to the Swedish coast, and between Zealand and Jutland lie many more islands, large and small. And this complex geography created a difficulty for Charles - how to transport an army of 10,000 men across the various straits between him and his quarry. But the weather came to Charles's rescue , and he accomplished one of the most daring feats ever to win a war: he walked across.
Europe at the time was in the middle of the Little Ice Age, and in late January Charles and his generals watched in eager anticipation as the temperature dropped and dropped, and a thick layer of ice began to form across the Kattegat. By February 9th, 340 years ago today, the ice was thick enough to attempt a crossing. The French ambassador again recorded his sensations: "It was terrifying to march at night across the frozen sea, since the multitude of horses that made their way caused the melting of the snow in such a manner that two feet of water was over the ice, and one feared all the time to find the open sea somewhere." But the ice held, and the following morning the Swedish forces were safely ashore.
The rest was easy. With the help of the ice, Charles used the Danish islands as stepping stones to Copenhagen, while the Danes - and indeed the rest of Europe - looked on in amazement. By February 21st he had reached the main island of Zealand, the Danes wisely sued for peace, and Sweden's dominant position in northern Europe was consolidated for some years to come.