Philip H. Jacobsen


Jacobsen, Philip H. [LTCDR/USN (Ret.)] "'Day of Deceit': An Analysis by a Veteran Navy Cryptologist." Cryptologia 24, no. 2 (Apr. 2000), 110-118.

With no small touch of sarcasm, Jacobsen notes that "through his exceptional foresight, unique expertise and diligence, Stinnett was able to see through [President Roosevelt's] monstrous conspiracy and its cover-up to reveal its details to us some 58 years later when all previous efforts by revisionist conspiracy theorists have failed and all the participants are dead and cannot defend themselves....

"[Although] Stinnett came up with many new documents not generally known to be available..., these documents do not add anything new to the question of who knew what and when. In his zeal, Stinnett misinterprets not only these documents but comes up with new meanings for the plain words and characterizations of well accepted documentation already available in this Pearl Harbor arena."

Jacobsen declares Stinett's theory to be unproven and an "impossibility," and makes his conclusion clear: "No U.S. officials knew beforehand of the Japanese plans to attack PH or discovered that the Kito Butai was on its way to Hawaii."

Clark comment: Jacobsen's review deserves to be read in full to get the flavor of some of the "gross omissions, errors and misinterpretations that Stinnett had to assemble to try to make his revisionist conspiracy theory seem plausible to the uninitiated."


Jacobsen, Philip H. [LTCDR/USN (Ret.)] Eyewitness to History. Pensacola, FL: U.S. Navy Cryptologic Veterans Association, 2006.

According to Kruh, Cryptologia 31.2 (Apr. 2007), this book includes a number of Jacobsen's "interesting" and "outstanding" articles on various aspects of World War II. This "is an excellent book for anyone interested in the U.S. Navy's role" in the war.


Jacobsen, Philip H. [LTCDR/USN (Ret.)] "Foreknowledge of Pearl Harbor? No!: The Story of the U.S. Navy's Efforts on JN-25B." Cryptologia 27, no. 3 (Jul. 2003): 193-205.

The author attacks the revisionist conspiracy interpretations of pre-Pearl Harbor events by Stinnett, Day of Deceit (1999) and Wilford, Pearl Harbor Redefined (2001). Jacobsen states: "When all the revisionist chaff is separated out, there is no credible evidence that Corregidor produced JN-25B decrypts of intelligence value, much less any cryptanalytic intelligence on the Kido Butai, prior to 7 December 1941.... It is abundantly clear that revisionist allegations that pre-war Corregidor decrypts of JN-25B messages provided a forewarning of the Japanese attack are completely and utterly unfounded."


Jacobsen, Philip H. [LTCDR/USN (Ret.)] "No RDF on the Japanese Strike Force: No Conspiracy!" International Journal of Intelligence and Counterintelligence 18, no. 1 (Spring 2005): 142-149.

"[N]ot one single radio direction finder bearing, much less any locating 'fix,' was obtained on any actual Kido Butai unit or command during its transit ... to Hawaii."


Jacobsen, Philip H. [LTCDR/USN (Ret.)] "Pearl Harbor: Radio Officer Leslie Grogan of the SS Lurline and His Misidentified Signals." Cryptologia 29, no. 2 (Apr. 2005): 97-120.

"[A]nalysis of Grogan's many conflicting stories ... shows that the reported signals, at best, were only plain language messages in the Japanese telegraphic code between Yokohama and the huge Japanese commercial fleet that had bunched up in home waters just prior to the initiation of hostilities."


Jacobsen, Philip H. [LTCDR/USN (Ret.)] Ed., Colin Burke. "Radio Silence of the Pearl Harbor Strike Force Confirmed Again: The Saga of Secret Message Serial (SMS) Numbers." Cryptologia 31, no. 3 (Jul. 2007): 223-232

In this posthumously published article, Jacobsen argues that an analysis of the SMS numbers confirms that "there were zero Strike Force transmissions." Therefore, there could be "no concurrent Allied DF bearings and/or 'fixes'" showing the Strike Force's ultimate goal.


Jacobsen, Philip H. [LTCDR/USN (Ret.)] "Radio Silence and Radio Deception: Secrecy Insurance for the Pearl Harbor Strike Force." Intelligence and National Security 19, no. 4 (Winter 2004): 695-718.

"[T]here is no evidence whatsoever to back up revisionist ... theories or suspicions that high level US, British or Canadian officials had advanced knowledge of the Japanese plans to attack Pearl Harbor ... and consequently no Washington official withheld such non-existent information from Hawaiian officials for political purposes."


Jacobsen, Philip H. [LTCDR/USN (Ret.)] "Station AL -- Guadalcanal: A Full Service WWII Cryptologic Unit." Cryptologia 31, no. 1 (Jan. 2007): 57-75.

The DF station on Guadalcanal went operational on 15 September 1942. On 5 November 1942, the personnel (including the author) arrived to establish a "small intercept, cryptanalysis, traffic analysis and reporting unit." The article has details about the work and life of the unit under dangerous and trying conditions.

[WWII/U.S./Services/Navy & Battles/Guadelcanal]

Jacobsen, Philip H. [LTCDR/USN (Ret.)] "Who Deceived Whom?" Naval History 17, no. 6 (Dec. 2003): 27-31.

"A review of newly declassified U.S. naval communications intelligence (ComInt) records refutes attempts by revisionist conspiracy theorists to 'prove' President Franklin D. Roosevelt knew of the Japanese plan to attack Pearl Harbor and withheld information to draw the United States into the European war. Evidence now corroborates a long-held view that Japanese radio deception masked movement of their carriers ... effectively ensuring a surprise attack."

Stinnett, Naval History 18.3 (Jun. 2004), takes issue with Jacobsen's analysis. Jacobsen replies in Naval History 19.1 (Feb. 2005).


Return to J-Jac