Complex sentence: Ski warfare, the use of ski-equipped troops in war, is first recorded by the Danish historian Saxo Grammaticus in the 13th century, who were reportedly able to cover distances comparable to that of light cavalry.
Split into simpler sentences: 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.