For countless generations, weather has influenced the planning and conduct of military and naval campaigns. In his instructions to his generals, Frederick the Great wrote, "It is always necessary to shape operation plans... on estimates of the weather." Since soldiers and sailors in combat have little or no protection from the weather, commanders have often scheduled their campaigns for those periods when storms and weather were considered less likely to disrupt operations.

For centuries, commanders conducted their campaigns during seasons that allowed their soldiers and horses to forage for food and fodder. The onset of winter invariably halted campaigns and often resulted in armies' returning home or seeking shelter for the winter. Since armies lacked massive supply systems, commanders had little choice but to schedule their campaigns to take advantage of harvests. Napoleon, for example, timed his invasion of Russia in 1812 so his soldiers could forage successfully. Though the emperor planned on using larger supply trains than in previous campaigns, he knew his huge forces could not carry all the food and fodder they required. Despite these preparations, Napoleon eventually lost more men to weather conditions, famine, and disease than to the Russian army.

The chance factor of weather has also influenced the result of individual battles. Weather played a key role, for example, in the Battle of Waterloo, for the battlefield became so soaked by heavy rains that Napoleon delayed his customary early attack so the ground would dry enough for cannonballs to ricochet and for cavalry to have secure footing. That delay of only a few hours provided Marshal Gebhard von Bl[udie]cher sufficient time to rush three Prussian corps forward and strike Napoleon's flank.

Throughout history, commanders have sometimes surprised their opponents by attacking when the season or weather caused them to lower their guard. During the winter of 1776, the British scattered their army in the American colonies in small garrisons, and on December 25, George Washington surprised the Hessian garrison at Trenton, New Jersey. He managed to get sufficient forces across the Delaware River, even though the weather was so severe that it kept some units from crossing. At the cost of four wounded, the Americans captured 948 Hessian soldiers and killed or wounded another 114.

During World War II, weather forecasts played a decisive role in the scheduling of the amphibious landing in Normandy (see D-Day). The invasion was initially scheduled for June 5, but an unfavorable weather report anticipated thoroughly nasty seas and gales of up to forty-five miles an hour. A break in the weather on the next day enabled the Allies to land and, according to Dwight D. Eisenhower, proved "the existence of an almighty and merciful God." An unanticipated benefit of the bad weather was that it helped the Allies achieve almost complete surprise.

In the Ardennes in December 1944, the Germans also used the weather to their advantage. Adolf Hitler coordinated the launching of the Battle of the Bulge very carefully and did not initiate the attack until he knew stormy weather would cause the Allied ground troops to lower their guard and the Allied air forces to fly for fewer hours. Because of the extremely cold weather, some of the American commanders had left minimum forces in the forward foxholes of the previously quiet sector and let some of their soldiers find shelter in nearby houses. When the skies finally cleared, however, defeat of the German forces soon followed.

Weather has had a strategic effect, as well as an operational and tactical impact. It played a decisive role in the Mongol invasion of Japan in 1281 when Kublai Khan attacked Kyushu with some forty-four hundred ships and 140,000 troops. Before the entire invading army landed, a typhoon struck the coast of Kyushu and destroyed half of the ships and men. Most of the Mongols remaining on Kyushu were slaughtered by the Japanese or drowned as they attempted to flee on the small vessels that escaped destruction. The Japanese viewed the typhoon as a "divine wind" (kamikaze) sent by the gods to save Japan and concluded that Japan was a "divinely protected land."

Storms also greatly influenced the fate of the Spanish Armada in 1588. Weather affected the naval campaign early, for shortly after the Spanish fleet departed Lisbon in May 1588, a storm scattered the Armada; it took a month to reassemble the ships and to recondition them. Favorable winds carried the Armada through the English Channel, but skillful English fighting forced the ships to make their way into the North Sea. After the Spanish passed by the northern coast of Scotland and entered the Atlantic, thirty-five to forty ships foundered in heavy storms, and another twenty smashed against the rocky shore. The victors inscribed on one of their victory medals Flavit Deus, et dissipati sunt (God blew and they were scattered).

ROBERT A. DOUGHTY

The Reader's Companion to Military History. Edited by Robert Cowley and Geoffrey Parker. Copyright © 1996 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.