Gordon Welchman: the architect of 'Ultra' intelligence

His pioneering work was fundamental to the success of Bletchley Park through his visionary new approaches to the science of decoding encrypted messages using machines.

By Bletchley Park

Gordon Welchman and Katharine Hodgson (1937)Bletchley Park

Who was Gordon
Welchman?

In the months before World War Two, the head of the Government Code and Cypher School (GC&CS) requested that Gordon Welchman, a lecturer in algebraic geometry and Dean at Sidney Sussex College, Cambridge, make himself available for secret work for the Foreign Office in the event of war.

Bletchley Park Mansion (1937)Bletchley Park

In March 1939 Welchman attended a course on the principles of cryptography, and on the 4 September 1939 he arrived at Bletchley Park where he worked in a senior management role throughout World War Two.

The SIXTA team at Bletchley ParkBletchley Park

Welchman at Bletchley
Park

In his first two months at Bletchley Park, Welchman independently reinvented a key part of the pre-war work of Polish cryptographers. He also laid the foundations for SIXTA, a fusion of traffic analysis - analysing patterns in communication - and cryptography - the practice of coding and decoding messages. 

Quote from Gordon WelchmanBletchley Park

Control Room Hut 6Bletchley Park

Welchman made key contributions to the ultimate success of Bletchley Park:

He was one of the first to recognise the need for a rapid expansion of the organisation’s infrastructure for the decryption and analysis of intercepted Enigma traffic and drew up an organisational forward plan...

...He also established ‘Hut 6’, which decrypted raw messages, intercepted from the German Army and Air Force and encrypted using the Enigma machine, as well as German Railway and SS traffic.

Front view of a Bombe machine, date unknown.Bletchley Park

Welchman and Alan Turing invented the Bombe, a machine that helped speed up the decryption of messages encrypted using the German Enigma machine.

Welchman’s invention, the ‘diagonal board’, improved the Bombe and allowed the decryption process to be scaled up.

"Most Secret" stampBletchley Park

After Winston Churchill’s visit to Bletchley Park in September 1941, Welchman wrote a letter, signed by Alan Turing and colleagues, expressing concerns about their lack of resources.

Churchill responded, ‘Make sure they have all they want on extreme priority’, adding: ‘Action this day’.

In 1943 Welchman was given responsibility for all ‘machine’ developments at Bletchley Park.

This included secure encryption devices and technical liaison with US cryptographic agencies.

Quote from Milner-Barry's obituary of WelchmanBletchley Park

Gordon Welchman's USA passportBletchley Park

Post-war work

After the war Welchman took up the post of Director of Research for John Lewis and Co. In 1948 he decided to emigrate to the United States and initially played a key role in Project Whirlwind, an ambitious project at Massachusetts Institute of Technology, which would deploy computers in air traffic control and air security for the first time. 

Welchman in Paris (1972)Bletchley Park

Welchman gave the first course of lectures on digital computer programming for the Electrical Engineering Department at Massachusetts Institute of Technology.

He worked on the US and UK’s development of digital computers (1948-52) and in Information Science (1956-62).

In 1962 Welchman joined the MITRE Corporation, which gave technical assistance to the United States Air Force, to help monitor airspace and deal with potential threats.

When Welchman retired in 1971, his research and inventions sat at the heart of US air defence.

Cover of 'The Hut Six Story' by Gordon Welchman (2nd revised ed., 1997)Bletchley Park

The Hut Six Story

Welchman's 1982 book, ‘The Hut Six Story’ revealed how German communications were intercepted by Britain’s Y Service and read by the Codebreakers at Bletchley Park. After Frederick Winterbotham’s book ‘The Ultra Secret’ came out in 1974, Welchman was released from his wartime pledge of secrecy - something that had given him great discomfort. 

Letter from Sir Peter Marychurch, head of GCHQ (1985-07-12)Bletchley Park

‘The Hut Six Story’ revealed in detail how the Codebreakers had read encrypted German messages on an industrial scale.

Its revelations caused a stir at the UK Government Communications Headquarters (GCHQ), and at its US counterpart, the National Security Agency (NSA).

Welchman and family (1972)Bletchley Park

Today, Welchman’s vision for a secure tactical communication system became a reality - the Joint Tactical Information Distribution System (JTIDS).

It's a command and control system used by the armed forces of NATO and many countries.

Welchman died on 8 October 1985 at the age of 79 in Newburyport, Massachusetts, USA.

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