The Battle of Midway Roundtable






Stealing the Enemy’s Secrets


Lt. Commander Philip H. Jacobsen, USN-Ret


by Ronald Russell


(The following originally appeared in Veterans Biographies, distributed during the annual Battle of Midway commemoration in San Francisco, June 2006)



Upon graduation from high school in 1941, Phil Jacobsen knew that he wanted a career in radio electronics, but there was no money in his family for college.  He turned to the Navy as a training resource, and succeeded in getting into radio school after boot camp.  Freshly trained in radio operation, equipment maintenance, and message handling procedures, his class was sent to Pearl Harbor where the Navy decided the new radiomen could best serve as laborers at the ammunition depot!  Jacobsen and several others were rescued from that drudgery when CDR Joseph Rochefort, in charge of the Combat Intelligence Unit at Pearl Harbor, directed the expansion of Japanese intercept operator training to support his growing cryptologic operation.

            The new intercept operators were trained at Wahiawa, in the center of Oahu.  They were immediately immersed in learning the 48-character Japanese equivalent of Morse code, as well as both the katakana and romaji variants of written Japanese.  In time they became proficient on a special typewriter that printed romaji characters, and were also taught Japanese communications procedures, message formats, and operating signals.  The also learned radio direction finding techniques.

            By May of 1942, RM3/c Jacobsen had completed training and was standing watches at radio intercept “Station H” at Wahiawa. The operators were informed of the possibility of a forthcoming large-scale Japanese operation, and to be extremely alert for any unusual activity or ship’s movements.  Enemy message traffic gradually increased in level as the month progressed giving a further clue to the radiomen that something big was in the wind.  Jacobsen recalls seeing the officer in charge at Station H and his chief radioman examining a chart with two tracks of ships converging on Midway.

            The skills practiced by RM3/c Jacobsen and his comrades at Wahiawa during that time provided a vast quantity of remarkably clear raw material for CDR Rochefort’s cryptanalysts at the Combat Intelligence Unit.  There the Japanese signals were decrypted and analyzed, leading to an extraordinary understanding of the Imperial Japanese Navy’s intentions at Midway weeks in advance of the attack.  That enabled Admiral Nimitz to plan what was to become the greatest American naval victory of all time.  There are many reasons for the triumph at Midway, principally centered on the incredible bravery of the men manning the guns and flying the planes as the battle raged.  But the success achieved there started with a few enlisted radiomen capturing the intelligence from the airwaves that made the victory possible.

            Late in 1942, Jacobsen transferred to Guadalcanal with a team that established a new radio intercept and cryptologic unit there as the battle for the Solomon Islands raged, and he served at other Pacific sites as the march toward Japan continued.  He retired from the Navy in 1969 after 28 years of service, nearly all in communications intelligence.



Photo of Phil Jacobsen


Navy Cryptology at the Battle of Midway: Our Finest Hour   (More about the communications intelligence victory at Midway, by Phil Jacobsen)


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