During the Great Northern War, the Swedish invasion of Russia led by Charles XII of Sweden against Russia's Peter the Great was notably weakened by the severe winter. Sudden winter storms and frosts killed thousands during the Swedish army's winter offensives, most notably during a single night away from camp that killed at least 2,000. Because the Russian troops were more prepared for the harmful weather and cautiously stayed within their camps, their losses were substantially lower, contributing heavily to their eventual victory at Poltava the following summer.