Probably since the days when the first spear was thrown in anger at another human, weather has played some role in warfare. Almost all of the fighting occurs during fair weather. It's just harder to fire weapons, whether they're catapults or howitzers, if it's windy or wet. On the other hand, bad weather is used as a cover, for example, as a means to move troops without detection. You fight in good weather, and in bad weather, well, you wait for better weather. During the Civil War, for example, the action basically stopped during the winter months. That was the case in the past, and to some degree, it's true today. Of course, with modern technology such as, geopositioning systems, radar, laser ranging, etc., weather is not the issue it was in year's past. Even so, when laser systems are employed in Afghanistan, the target needs to be seen visually - overcast skies render them useless.

As recently as early September, when the terrorist attacked the World Trade Center and the Pentagon, weather played a role in the outcome. The skies were perfectly clear over Boston, New York and Washington when the terrorists hijacked those commercial jets. Who knows whether they were waiting for just such a day, but they probably weren't even capable of taking off or landing a jet, so there's no way they could fly one "on instruments." If it was foggy or cloudy over New York City or DC on September 11, they may have missed their targets all together, or perhaps they would have changed their plans and waited for a different day.

In the Hawaiian Islands, although it can be like a tropical paradise on many days, there's a seasonal component to the weather. It tends to be warmer, windier and drier from about April through September. This is the time when the trade winds blow almost constantly from the east and northeast. From October through March, it's wetter. In fact December and January are the two wettest and cloudiest months on Oahu, so it's unlikely that the Japanese planned their attack based on climatology. Nevertheless, weather worked to their advantage.

Winter is when the "Kona" storms and frontal rains occur most frequently. "Kona" is the term applied to widespread rainstorms that approach Hawaii from any direction other than the direction that the "trades" blow. The "trades" still blow this time of year, but because during the course of the year, the zone of the trade winds move north and south with the Sun, they're typically positioned a little further to the south in winter than during the summer.

Rather than head directly toward Hawaii, the Japanese Fleet had moved northeast from the main island of Honshu to the Kuril Islands (northeast of the island of Hokkaido). This route was chosen since the prevailing weather conditions in the northwest Pacific are generally cloudy in late autumn. The bad weather that greeted the Japanese Fleet lessened the chance that the they would be detected by the US and its allies. In late November, the fleet steamed from the Kuril Islands to their destination, north of Hawaii.

At 5 minute before 8:00 in the morning of December 7, 1941, Japanese airmen took off from the fleet's 6 aircraft carriers and attacked Pearl Harbor, where the US Pacific Fleet was moored (on the Hawaiian island of Oahu). The day of the week, Sunday, was chosen because it was known by the Japanese that the American Fleet, after training at sea, returned to Pearl Harbor on weekends. It happened that this Sunday dawned sunny. The forecast was for partly cloudy skies, but mostly cloudy over the mountains, but elsewhere, the visibility was good - the winds were from the north at 10 mph.

From the Japanese point of view, a more favorable situation could not have been asked for. The Japanese aircraft carriers were concealed by thick clouds in the waters about 230 miles north of the Hawaiian Islands. Once in the air, the pilots weren't able to see the water because of the clouds and pre dawn darkness. In fact, they honed in on their target by listening to music on a Hawaiian radio station - they had been off target by approximately 5 degrees before their course was corrected. At approximately 7:30, as the pilots neared the north coast of Oahu, the clouds broke, and the Japanese pilots had nearly a clear view of Pearl Harbor and the "sitting ducks" of the US Pacific Fleet.

Although it started out as a beautiful Sunday morning in Paradise, by mid morning more than 2,400 US soldiers, sailors and civilians had lost their life, and more than 1,100 were injured. Seven of the 8 battleships in Pearl Harbor were sunk or crippled by the bombing.

Though not directly weather-related, weather did play another role in the Pearl Harbor attack on December 7. On December 4, an intelligence office outside of Washington D. C. was monitoring the news from Radio Tokyo, as he did everyday. What he heard seemed to be nothing more than a routine weather forecast, the kind that were heard every day during their morning broadcasts - "east wind, rain.". But the officer knew what these three words meant.

This phrase was a possible "execute" message that Japanese diplomats around the world had been alerted to begin listening for in mid November. They were told to monitor the regular news and weather broadcasts from Tokyo, just as they always did, but to pay especially careful attention to the phraseology employed to describe the weather. If they heard the words "east wind, rain," it means war with the United States. The US intelligence officer knew this and he immediately teletyped the message to Washington.

At the Japanese Embassy, the Chief Petty Officer also was listening to the weather report. When he heard those fateful words "Higashi no kaze ame" - "east wind, rain". He rushed into the office of the naval attaché and shouted "The winds blew". Quickly, the workers at the embassy began destroying their cryptographic equipment and code books, while others took the secret documents from their files and burned them.

Meanwhile, almost half way around the globe, Hitler was elated by the news of the Japanese attack on the US. On December 11, Germany and Italy declared war on the US. However, the German's were finding out how just how brutal a Russia winter could be, and how quickly the winds of war could change. Russia was experiencing what turned out to be one of it's coldest December's on record. During the first week of December 1941, the German Army continued to attack Russia, but the temperature had dropped to -30 F (almost -35 C)! German tanks, guns and other equipment were frozen, and thousands of troops in thin, leather boots and lightweight uniforms suffered terrible frostbite.

The US was forced in war on two fronts in different hemispheres. Within a week, 35 nations representing half the world's population were at war - the second great war of the century was underway.