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Information Warfare

Naval Security Group Disestablishment

A Brief History for the Naval Security Group Command Disestablishment Ceremony

30 September 2005

Navy cryptology began in 1924 in the Department of Naval Communications under LT (later Captain) Laurence Safford who had an intuitive understanding of the importance of radio (still new) intelligence in future conflicts. He recruited a handful of subordinates, the most famous of whom was LT (jg) Joseph Rochefort.

The group was re-designated OP-20-G as a secret staff under the Director of Naval Communications. They began training significant numbers of intercept operators in how to copy and analyze encrypted Japanese Navy communications in 1928. They were led and trained by the hard-charging Chief Radioman Harry Kidder.

OP-20-G was hidden in a shed on the roof of the Navy Department Building in Washington, DC. Those in the group became know as the “On the Roof Gang.”

In 1930 graduates were already serving in the Pacific and Asiatic Fleets conducting radio intelligence operations against the Japanese Navy. US Admirals were deeply impressed with their code breaking and analytic skills.

The exploits of the On the Roof Gang ran the gamut from clandestine missions in Japanese territorial waters to covert collection from US diplomatic facilities in China. This force formed the nucleus of cryptologic operations in the looming war against Japan and Germany.

On the eve of WWII, CDR Joe Rochefort, who commanded Station Hypo in Honolulu, was the only Navy officer who was both a trained cryptanalyst and Japanese linguist. His office was understaffed, Germany was the higher priority target at the time, and as a result had not been able to crack the JN-25 main Navy Code before Dec 7 1941.

After failing to predict the raid on Pearl Harbor, Rochefort vowed to do whatever he humanly could to provide the Pacific Fleet with the information needed to defeat the Japanese.

By March of 1942 Rochefort and crew were breaking and reading JN-25 messages as fast as the intended recipients.

Rochefort was able to work out the time and location of the Japanese Navy’s cross-Pacific offensive. Admiral Nimitz put great stock in his work, gambled, and positioned his forces to intercept the enemy at Midway. The US victory in that epic battle turned the tide of the war in the Pacific.

In a team effort with Great Britain and the Royal Navy, Navy Cryptologists worked round the clock with a workforce of thousands, 80% of it women, to crack the German U-Boat Enigma codes to end deadly attacks on Allied convoys. They enjoyed great success and even defeated the far more sophisticated four-rotor version of Enigma called Shark. In so doing they saved thousands of tons of Allied shipping and thousands of lives.

At the height of the war, nearly 10,000 specialists were involved in the work of the Naval Security Group. WWII demonstrated the value for a standing force of trained cryptologists. In 1950 the Naval Security Group was established as an independent command.

Naval Security Group Cryptologists were involved in every major crisis of the Cold War and were involved in land, sea and air combat operations in the Korean War from the beginning in 1950. They served on ships, coastal craft, submarines, and SIGINT aircraft conducting covert collection against North Korea and China.

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