The document summarizes the Little Ice Age, a period from the 14th to 19th centuries when global temperatures dropped by 2-4 degrees Fahrenheit. This cooling was likely caused by increased volcanic activity, changes in ocean currents and melting glaciers, and reduced solar radiation due to fewer sunspots. The Little Ice Age led to failed crops in Europe and disease, contributing to the death of one-third of the European population. It also encouraged reasons for wars and destroyed a large part of the Spanish Armada. Napoleon's 1812 invasion of Russia was unsuccessful as the Russians destroyed food and water supplies, and only 40,000 of Napoleon's 500,000 man army returned due to illness, hunger and cold.