Oliver Strachey a British civil servant in the Foreign Office was a cryptographer from World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 to World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

.

He was a son of Lt-Gen Sir Richard Strachey

Richard Strachey

Lieutenant-General Sir Richard Strachey, GCSI, FRS , British soldier and Indian administrator, third son of Edward Strachey and grandson of Sir Henry Strachey, 1st Baronet was born on 24 July 1817, at Sutton Court, Stowey, Somerset...

 and Lady (Jane) Strachey, and a brother of the writer Lytton Strachey

Lytton Strachey

Giles Lytton Strachey was a British writer and critic. He is best known for establishing a new form of biography in which psychological insight and sympathy are combined with irreverence and wit...

. He was educated at Eton College

Eton College

Eton College, often referred to simply as Eton, is a British independent school for boys aged 13 to 18. It was founded in 1440 by King Henry VI as "The King's College of Our Lady of Eton besides Wyndsor"....

 and attended Balliol College, Oxford

Balliol College, Oxford

Balliol College , founded in 1263, is one of the constituent colleges of the University of Oxford in England but founded by a family with strong Scottish connections....

 for one term (Hilary

Hilary term

Hilary Term is the second academic term of Oxford University's academic year. It runs from January to March and is so named because the feast day of St Hilary of Poitiers, 14 January, falls during this term...

 1893). According to Who was Who he was in the Foreign Office, and engaged in work on East Indian Railway and historical research. He co-authored with his wife Ray a work on Keigwin’s Rebellion (1683–84), an episode in the history of Bombay; it was published in 1916.

His first marriage to Ruby Julia Mayer produced one daughter, Julia Strachey

Julia Strachey

Julia Strachey was an English writer, born in Allahabad, India, where her father, Oliver Strachey, the elder brother of Lytton Strachey, was a civil servant. Her mother, Ruby, was of Swiss-German origin...

, and ended in divorce. In 1911, he married Rachel Conn (Ray) Costelloe

Ray Strachey

Ray Strachey, née Costelloe was a British novelist, born Rachel Costelloe in London, England.-Early life:She is the elder of the two girls in her family...

 (1887–1940). They had two children Christopher

Christopher Strachey

Christopher Strachey was a British computer scientist. He was one of the founders of denotational semantics, and a pioneer in programming language design...

 and Barbara. Christopher Strachey later became a pioneer in the development of computers and computer languages.

In World War I, he was in British Military (Army) Intelligence, MI1

MI1

MI1 or British Military Intelligence, Section 1 was a department of the British Directorate of Military Intelligence, part of the War Office. It was set up during World War I...

. Between the wars, he was in the Government Code and Cypher School. In 1934, Strachey and Hugh Foss

Hugh Foss

Hugh Rose Foss was a British cryptographer.-Life:Foss was born in Kobe, Japan, where his father the Rt Revd Hugh Foss was a missionary bishop, and he learned Japanese....

 broke the Japanese naval attaché machine cipher.

In World War II, he was at Bletchley Park

Bletchley Park

Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing...

. He headed the ISOS section deciphering various messages on the Abwehr network involved with turned German agents (part of the Double Cross system

Double Cross System

The Double Cross System, or XX System, was a World War II anti-espionage and deception operation of the British military intelligence arm, MI5. Nazi agents in Britain - real and false - were captured, turned themselves in or simply announced themselves and were then used by the British to broadcast...

), with the first decrypt issued on 14 April 1940. Initially codenamed Pear, the decrypts became known as ISOS, standing either for Illicit or Intelligence Services (Oliver Strachey). He was replaced as head of ISOS by Denys Page

Denys Page

Sir Denys Lionel Page was a British classical scholar at Oxford and Cambridge.-Early life:Born at Reading, Page was the son of Frederick Harold Dunn Page, a chartered civil engineer of the Great Western Railway, and his wife Elsie Daniels. He was educated at St...

 in early 1942.

In January 1942, Strachey went to Ottawa, Canada, where he was chief cryptographer in the Examination Unit, where he remained until July. This ambiguously named, top secret cypher department was the Canadian version of Bletchley Park. His predecessor at the Unit was the notorious Herbert Osborne Yardley, who had written a sensational expose of American and British cryptography in World War I, "The American Black Chamber" (1931). Yardley's contract was not renewed under pressure from Washington. Strachey refused to go to Ottawa until Yardley had left the city.

Strachey brought with him from England keys to high-level French Vichy

Vichy

Vichy is a commune in the department of Allier in Auvergne in central France. It belongs to the historic province of Bourbonnais.It is known as a spa and resort town and was the de facto capital of Vichy France during the World War II Nazi German occupation from 1940 to 1944.The town's inhabitants...

 and Japanese diplomatic codes, which initiated close cooperation with Washington and London. Although he did not speak or read Japanese, he helped break the Japanese encryption, which was very complex, since it used variations of kanji, hiragana, and romanization. At 67, he "was a man whose best work has been done."

His recreations were music and reading. He was awarded a CBE

CBE

CBE and C.B.E. are abbreviations for "Commander of the Order of the British Empire", a grade in the Order of the British Empire.Other uses include:* Chemical and Biochemical Engineering...

in 1943.