Station HYPO

[2] The precise importance and role of HYPO in penetrating the Japanese naval codes has been the subject of considerable controversy, reflecting internal tensions amongst US Navy cryptographic stations.

The US Army's Signals Intelligence Service (SIS) broke into the highest level Japanese diplomatic cypher (called PURPLE by the US) well before the attack on Pearl Harbor.

Wilford in his Decoding Pearl Harbor: USN Cryptanalysis and the Challenge of JN-25B in 1941, suggests that this view is now untenable and that the JN-25 codes were readable to a great extent and hence, lends "support to the revisionist theories of Toland and Stinnett".

Hong Kong's contribution stopped until the crypto station there could be relocated (to Ceylon and eventually Kenya), but HYPO and the Dutch at Batavia, in conjunction with CAST and OP-20-G made steady progress.

The center on Corregidor (CAST) was no longer affiliated with a fleet command, and its collection and processing capabilities were rapidly disintegrating as a result of evacuations of personnel to Australia and destruction of its facilities by bombing and gunfire.Japanese traffic was intercepted regarding a new offensive operation being planned against a target only identified as AF.

In October 1942, after Midway, power struggles within the Navy resulted in the sidelining of Laurance Safford, with the support of Admirals Ernest King and Richmond K. Turner (and Joseph Redman).

Safford was shifted to an administrative support and cryptographic research role; so was sidelined for the remainder of the war (doing no further crypto work); as was Joseph Rochefort in Hawaii (he was assigned to command a dry-dock on the West Coast).

Rochefort was posthumously awarded the medal after a campaign by his intelligence officers galvanized Admiral D. "Mac" Showers and eventually CIA head William Casey to rectify the oversight.