Home   Genealogy   Forums   Search   Contact
MHO Home
MHO Home
 17th Century
 18th Century
 19th Century
 American Civil War
 World War I
 World War II
 20th - 21st Century

 Write for MHO
 Search MHO
 Civil War Genealogy Database
 Privacy Policy

Pearl Harbor Sections
MHO Home
 WWII Home
  Pearl Harbor Home
   Magic <<<
   Tiger, Tiger, Tiger
   "No, sir. This is Pearl."
   "The results…what are they."

WWII Sections
MHO Home
 WWII Home
  Eastern Front
   Polish Campaign
USSR invades Poland
USSR attacks Finland
Yugoslavia and Greece 
Operation Barbarossa
   Blitzkrieg across USSR
Operation Blue
   Warsaw Uprising
Operation Bagration
Battle of Berlin
  North African and Mediterranean 
El Alamein
Operation Torch
Kasserine Pass
Tunis Falls
   Allied Landings in Italy
Germany forces in Italy surrender 
  Western Front
   The Phoney War
Norway and Denmark Campaigns
The Low Countries
Fall of France 
   Raid on Dieppe
   The Atlantic Wall
   D-Day (Normandy)
   Allied Breakout
   Liberation of France
Operation Market Garden
Battle of the Bulge
Rhine Crossing
Fall of Germany
  The Air War  
   The Blitz
   Bomber Command
   Battle of Britain
The V1 and the V2
  Battle of the Atlantic  
   Battle of the River Plate
Bismarck vs. Hood
Channel Dash
   Battle of the Barents Sea
   Battle of North Cape
  War in the Pacific  
   Pearl Harbor
   Battle of Java Sea
Battle of Coral Sea 
Battle of Midway
   China Airlift 
   Battle of Bismarck Sea
Battle of Phillippine Sea 
   Battle of Leyte Gulf
Iwo Jima 
   Hiroshima and Nagasaki 
Japan Surrenders
Pearl Harbor - Magic
Pearl Harbor - "Magic" 
by Gregory Karpicky

The Americans had not been idle during the build up to the Pacific conflict. As early as the twenties, American and British cryptanalysts had forged an agreement. As the British had a lead in deciphering Japanese naval codes, they would concentrate their efforts on those while the Americans would work on diplomatic codes.

By 1939 the Americans had finally broken the Japanese diplomatic code that would eventually become known as "Purple". "Purple" enabled President Roosevelt and his staff to be privy to Foreign Minister Oshima's communications to Ambassador Nomura. This gave the U.S. an invaluable advantage in reading diplomatic messages. But that advantage did not translate into an advantage in naval intelligence or intentions in the Pacific. The Japanese militarists, by this time fully in charge of the Japanese government, were dead set on a war with Britain and the U.S. and did not want their embassies to know. So while Foreign Minister Oshima may have known more than he let on, he certainly did not communicate that to his ambassadors.

By the fall of 1941 the English had finally deciphered about one tenth of JN25. But that allowed a lot of information to slip through the cracks. Also the Japanese at that point were changing ciphers about every ten days and being very careful with military radio traffic. The Japanese navy had also recently changed call signs on all their ships and only about 20% of the fleet had been identified by December 7th. However, they then reassigned individual radio operators, so Allied intelligence would recognize their "fists" and believe the ship's location: i.e., that ships they were assigned to were in southern Japan and not in the northern Pacific.

On November 29th the famous "Winds" message was sent, warning that conflict with Britain, the United States, or the Soviet Union may break out soon. If any eventuality were to take place and normal communications could not be used, a simple, coded message, disguised as a weather report, would be broadcast over Japanese radio:

"In case of danger with Japan-U.S. relations, the words: higashi no kaze, ame (East wind, rain)

Japan-Soviet relations, the words: kita no kaze, kumori (North wind, cloudy)

Japan-British relations, including invasion of Thailand, the words: nishi no kaze, hare (Westerly wind, fine.)

This signal will be given in the middle and at the end as a weather forecast and each sentence will be repeated twice. When this is heard please destroy all code papers, etc." [1]

While most sources say that the message to initiate action was never received, there are at least two that say it was. One was a Michael Smith, who said that the "execute" was received late in December 7th Hong Kong time, (early December 7th West Coast time.) The other was an unnamed sergeant who never testified in any of the formal investigations. Even had the message been received and distributed, it would at most have given only a few hours to prepare. The battleships at Pearl would take that long just to raise steam.

But no one was thinking only of an attack on Pearl.  By early November the situation in the Pacific was grave enough for General George C. Marshall and Admiral "Betty" Stark to send a "war warning" [2] to the various commanders in the Philippines, at the U.S. Panama Canal Zone, and in Pearl Harbor. But the intelligence available indicated the Japanese were sailing south towards Malaya and Thailand. Conventional thinking at the time said that, if war broke out, the Japanese would secure their flank by attacking the Philippines as well, which they did. But there were no decrypted messages in "Purple" or JN25 that would lead either England or America to believe that Hawaii was the main target. By the time the Japanese had decided on war, American and British leaders were aware of an impending conflict, but did not know where it would begin.


[1]. Hearings before the Joint Committee on the Investigation of the Pearl Harbor attack, Congress o f the United States, Seventy-ninth Congress, p. 154.

[2]. At Dawn We Slept; Gordon W. Prange, p. 406.

- - -

Copyright © 2005 Gregory Karpicky.

Written by Gregory Karpicky.  If you have questions or comments on this article, please contact Gregory Karpicky at:

About the author:
My literary background has mostly been in writing for various businesses I have consulted for. My father was a career Army officer who earned the Legion of Merit, and the exposure I received at various postings around the world with this gave me a lifelong interest military history.

Published online: 12/17/2005.
< Previous Page

Next Page >

© 2016, LLC Contact Brian Williams at: