Codebreaking; 'The Determining Factor in the Conduct of the War'

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29 CODEBREAKING; 'THE DETERMINING FACTOR IN THE CONDUCT OF THE WAR’ NAKURK WATEUI SHUDAN to XGAN YTE NPKRKK ZLT SI NTOSURUM ONARUGA ATTENWASYRYONONIUTT Ailies decipher secrether RUMONORARUKOTOOHSHES ESITERKWGAW APOL'S neny .codes, 1942 25URYO KOOM 17 1992 KURIL se votos rO SEARC pte OR JUNE 46206 00 FLET er a g e Tatae seant roRc TF-16 BONN ST FORe-an a te SEEOND FLEET Sa GGGG MARSHALL ISLANDSs Chis lalle Ocooo IN INDIA

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ALLIES DECIPHER ENEMY SECRET CODES First Day of Issue: August 17, 1992 First Issue Location: Indianapolis, Indiana In 1939, the British successfully deciphered Enigma, Germany's secret code. This vital breakthrough proved invaluable to Britain in the Battle of the Atlantic and, later, to the Allies in Sicily and Normandy. Enigma's Japanese counterpart was Purple, a system which functioned on the fundamentals of a telephone switchboard. Purple pre- sented monumental challenges to the U.S. Intelligence Service, but in September of 1940, the War Department's chief cryptanalyst, Col. William Friedman, cracked the code. The American deciphering program served its coun- try most illustriously just before the Battle of Midway in 1942. Intercepted Japanese communications revealed that an enemy task force was moving on a target referred to as “AF." An American cryptanalyst set a telegraphic trap which confirmed that “AF” was Midway. Subsequent Japanese communiques also revealed the date of the enemy offensive — June 4. A prepared American naval force intercepted and devastated the attack force turning the tide of war in the Pacific for the Allies. No. 92-106 First Day of Issue Postcard Collection™ ©1992 Fleetwood® Cheyenne, WY 82008-0001 Original painting for the First Day of Issue Postcard by Chris Calle Fleetwood