How Weather Changed the Course of Wars

The Revolutionary War

Gen. George Washington and most of the American troops were in what is now New York City in the summer of 1776. In late August, the British landed a much larger number of troops in the area in preparation for an attack. On August 27, the British charged the Americans with a superior force. With the redcoats only a few hundred feet away, the American troops used the cover of dense fog to escape unnoticed, with Washington among the last to retreat. If not for that fog, historians believe, General Washington would have been captured and the war likely ended with American defeat.

In early 1777, Washington again faced disaster, as his troops were bogged down in New Jersey, surrounded by a superior British force, with muddy ground making movement nearly impossible. By nighttime, rain was falling, to be followed by strong northwest winds and temperatures holding steady and then even starting to fall during the day. Washington did not realize that this meant that a strong cold front had passed—he did not know about or understand the science behind cold fronts—but he did realize from his experience that this meant that the coming night would get much colder.

With this knowledge, Washington ordered his troops to prepare huge bonfires to make it appear as though they were holding their ground for the night. But, in the darkness, Washington had his troops prepare to evacuate—which they did as soon as the ground froze. In the darkness, with the ground frozen, Washington moved his troops, cannons, and other matériel northward to higher ground—thereby living to fight  another day.

If Washington had not used his knowledge of weather patterns to realize that the ground would freeze as the basis for his strategic retreat, his forces would have instead been surrounded and captured—and America would have likely lost its war for independence in 1777 instead of ultimately winning it in 1783, with the final peace accord signed at Yorktown, Virginia.

Soldiers evacuate from the beaches near Dunkirk, France, during World War II. Photo courtesy of the Imperial War Museum.

World War II

More than a century and a half later, during the early stages of World War II in 1940 when Axis forces were winning battle after battle, the main Allied force was trapped near Dunkirk, a town along the English Channel in northern France. A retreat or rescue was nearly impossible, since the superior German air force would have blown any ships out of the water.

But what Winston Churchill called “a miracle of deliverance” appeared, as heavy rains kept German planes grounded while calm waters and dense fog allowed the Allied forces to escape quietly, undetected, across the English Channel. As the last men were ferried to safety, the weather cleared, leaving the Germans alone on the beach and the Allies alive to fight another day.

Although Hitler and Stalin had signed a mutual nonaggression pact in 1939, by 1941 each country had plans to attack the other. Hitler struck first, in June of 1941. Recognizing the difficulties of Russian winters, Hitler’s plans were to defeat Russia by late fall. In fact, the German army was so confident that it could defeat Russia quickly that several units brought dress uniforms for a victory march in Red Square but did not bring any winter clothes.

But Hitler was not able to initially deploy as many troops as early in the fall as he had planned. It turned out that the troops of his ally, Italian dictator Benito Mussolini, were bogged down in North Africa, so Hitler had to bail him out. He dispatched German Gen. Erwin Rommel’s troops to Africa to prevent an Axis defeat, thereby delaying their deployment to Russia. The result was that the German troops were tired and less effective than Hitler had planned when they arrived on the Russian front. Then, heavy rains further delayed the German advance into Russia by a couple of weeks, which turned out to be crucial.

Now Germany was running well behind schedule, and despite all of Hitler’s initial planning to defeat Russia early, he wound up in the same Russian winter trap that had defeated Napoleon back in 1812—still fighting during what turned out to be the coldest Russian winter in 140 years with German soldiers unprepared for temperatures as low as 40° below zero.

Hitler’s defeats in the Soviet Union, outside Moscow and in Stalingrad, became an important turning point in the war—and they were largely due to the heavy rains that had delayed the invasion and then the extraordinarily cold winter. Ultimately, this weather sequence shortened the war and probably reduced American casualties substantially. Again, the weather seemed to be on America’s side.

In early June of 1944, the Germans still controlled most of Europe. Although they knew that the Allies were planning a major attack with a landing from the sea to establish a beachhead on the continent, the Germans did not know the exact timing or the location of the coming attack. The Allies had been planning this attack for more than a year and decided to launch the invasion on Normandy beaches in France on June 6, 1944—weather permitting.

Having broken the German Enigma code used to encrypt communications, the Allies were able to access and use German weather observations. This gave Allied meteorologists a weather advantage. Because they already controlled most of the Atlantic and thus knew the weather upstream over the Atlantic Ocean and across the UK, the Allies needed only to add knowledge of German weather conditions to have enough extra information to be able to advise the Allied commander, Gen. Dwight D. Eisenhower, that conditions for the planned invasion would be marginal, but sufficient.

In contrast, the Germans were without sufficient upstream weather observations. As a result, they were forecasting weather conditions unsuitable for an invasion that day, so they were caught completely by surprise by the Allied attack on Normandy beaches.

As with George Washington, for Dwight Eisenhower superior knowledge of weather conditions and forecasting ability were the keys to a critical victory. The success of the Normandy landing and this whole mission, of course, led not only to Germany’s defeat but also to a boost to Eisenhower’s reputation and career—which later helped him to become a two-term president of the United States.

See more ways weather may have changed the course of American history.