Cold-weather warfare, also known as arctic warfare or winter warfare, encompasses military operations affected by snow, ice, thawing conditions or cold, both on land and at sea. Cold-weather conditions occur year-round at high elevation or at high latitudes, and elsewhere materialise seasonally during the winter period. Mountain warfare often takes place in cold weather or on terrain that is affected by ice and snow, such as the Alps and the Himalayas. Historically, most such operations have been during winter in the Northern Hemisphere. Some have occurred above the Arctic Circle where snow, ice and cold may occur throughout the year. At times, cold or its aftermath—thaw—has been a decisive factor in the failure of a campaign, as with the French invasion of Russia in 1812, the Soviet invasion of Finland in 1939, and the German invasion of the Soviet Union during World War II. History Northern and Eastern Europe were the venues for some well-documented winter campaigns. During World War II several actions took place above the Arctic Circle. Recent cold-weather conflicts have occurred in the Himalayas. Pre–1800 In 1242, the Teutonic Order lost the Battle on the Ice on Lake Peipus to Novgorod. In 1520, the decisive Battle of Bogesund between Sweden and Denmark occurred on the ice of lake Åsunden. In 1643 or 1644, Prince Rupert made an abortive attack on the Parliamentarian stronghold of Aylesbury England. 500 men are reported to have frozen to death on 21 January. On 25 January a sudden thaw caused a bridge to collapse over the River Weaver, splitting Royalist cavalry forces at the Battle of Nantwich resulting in their defeat. The 1557 Siege of Katsurayama in was fought between the forces of the Japanese daimyō Takeda Shingen and Uesugi Kenshin as part of the Kawanakajima campaigns. Katsurayama castle was a strategically vital Uesugi stronghold in the contested Shinano Province and, when it was isolated from reinforcements due to late snow in early 1557, the Takeda clan used this opportunity to seize it under Baba Nobuharu, shielded from view by heavy snowfall. Sweden and Denmark fought several wars during the 16th and 17th centuries. As a great deal of Denmark consists of islands, it was usually safe from invasion, but in January 1658, most of the Danish waters froze. Charles X Gustav of Sweden led his army across the ice of the Belts to besiege Copenhagen. The war ended with the treaty