Station HYPO

The vision of this blog is to post quality content that celebrates the history of Naval Cryptology, keeps members of the Cryptologic community up to date on current events and development, and sparks discussion about our future.

Why Station HYPO?

During WWII Station HYPO played a significant role by providing time-sensitive intelligence to Admiral Nimitz and his commanders, giving them the tactical advantage they needed to defeat the Japanese Imperial fleet.  The support provided by Station HYPO was so reliable that Admiral Nimitz compared this special type of intelligence to having an additional fleet of ships.  We believe the same innovation, competence and collective ownership that permeated Station HYPO 85 years ago exists in our Cryptologic Enlisted Sailors and Information Warfare Officers today!

Station HYPO began in 1938, three years before the attack on Pearl Harbor, as the Hawaiian Decrypting Unit/Communication Intelligence Unit at the Pearl Harbor Navy Yard administration building.  In June 1941, five months before the attack on Pearl Harbor, CAPT Safford head of OP-20G in Washington DC assigned then LCDR Rochefort  as the Station HYPO Officer-In-Charge.  On December 1 1941, under the charge of LCDR Rochefort, the Decrypting Unit/Communication Intelligence Unit moved from the second floor of the Administration Building to the basement.  This was partly for security reasons, because the basement was sealed off from the rest of the building, but also to accommodate a growing staff, which had doubled from 23 in June to 47 in December.  Later in the same month, after the attack on Pearl Harbor, the unit was re-designated as the Combat Intelligence Unit and was given the classified code name Station HYPO.  At the time, HYPO was the phonetic code for “H” and was in direct reference to He’eia, Hawaii, the station’s location.

In April 1943, Station HYPO moved from the Pearl Harbor Navy Yard into a new two-story building at Makalapa, adjacent to the Commander-in-Chief Pacific Fleet (CINCPACFLT) headquarters where it remained for the duration of WWII.  In 1945 it became known as Naval Security Group Pacific and moved to the fourth floor building of the CINCPACFLT headquarters building at Makalapa until 1951.

Some of Station HYPO’s WWII contributions include, but not limited to:

• Established the Japanese Imperial Fleet organizational structure (Naval Order of Battle) and Command Control structure.
• Discovered that the Japanese Imperial Fleet radically reorganized days before the attack on Pearl Harbor and was attempting Radio Deception.
• Provided time-sensitive intelligence to Commander Submarine Pacific that resulted in the first sinking of a Japanese man of war (submarine) following the post Pearl Harbor attack.
• Provided intelligence on Japanese build up on their outer defense located on the Marshals and Gilbert Islands.
• Provided time-sensitive intelligence on the Japanese naval forces operating in the Coral Sea resulting in the battle of Coral Sea.  The intelligence provided gave Admiral Nimitz confidence in Station HYPO efforts.
• Provided accurate time-sensitive intelligence to Admiral Nimitz regarding the planned Japanese attack on Midway Island.  Admiral Nimitz repositioned his remaining aircraft carrier battle groups based on this intelligence alone.
• Provided time-sensitive intelligence on the location and movement of Admiral Isoroku Yamamoto, the Commander-in-Chief of the Combine Fleet, which resulted in the shoot down of his transport aircraft killing the Admiral.  Admiral Yamamoto was responsible for the attack on Pearl Harbor.