 Complete the following phrase:  Ski warfare, the use of ski-equipped troops in war, is first recorded by the Danish historian Saxo Grammaticus in the 13th century. These troops were reportedly able to cover distances comparable to that of light cavalry. The garrison in Trondheim used skis at least from 1675, and the Danish-Norwegian army included specialized skiing battalions from 1747details of military ski exercises from 1767 are on record. Skis were used in military exercises in 1747. In 1799 French traveller Jacques de la Tocnaye recorded his visit to Norway in his travel diary: Norwegian immigrants used skis Norwegian snowshoes in the US midwest from around 1836. Norwegian immigrant Snowshoe Thompson transported mail by skiing across the Sierra Nevada between California and Nevada from 1856. In 1888 Norwegian explorer Fridtjof Nansen and his team crossed the Greenland icecap on skis. Norwegian workers on the Buenos Aires - Valparaiso railway line introduced skiing in South America around 1890. In 1910 Roald Amundsen used skis on his 