Robert Conquest was born in Malvern, Worcestershire, the son of an American businessman and a Norwegian mother. His father served in an ambulance unit with the French Army in World War I, being awarded the Croix de Guerre in 1916. Conquest was educated at Winchester College, the University of Grenoble, and Magdalen College, Oxford, where he was an exhibitioner in modern history and took his bachelor's and master's degrees in Philosophy, Politics and Economics, and his doctorate in Soviet history.

In 1937, after his year studying at the University of Grenoble and traveling in Bulgaria, Conquest returned to Oxford and joined the Communist Party. Fellow members included Denis Healey and Philip Toynbee.

When World War II broke out, Conquest joined the Oxfordshire and Buckinghamshire Light Infantry and became an intelligence officer. In 1940, he married Joan Watkins, with whom he had two sons. In 1942, he was posted to the School of Slavonic and East European Studies, where he studied Bulgarian for four months.

In 1944, Conquest was posted to Bulgaria as a liaison officer to the Bulgarian forces fighting under Soviet command. There, he met Tatiana Mihailova, who later became his second wife. At the end of the war, he was transferred to the diplomatic service and became the press officer at the British embassy in Sofia, Bulgaria. He witnessed the gradual rise of Soviet communism in the country, becoming completely disillusioned with communist ideas in the process. He left Bulgaria in 1948, helping Tatiana escape the new regime. Back in London, he divorced his first wife and married Tatiana. This marriage later broke down when Tatiana was diagnosed with schizophrenia.

Conquest then joined the Foreign Office's Information Research Department (IRD), a unit created for the purpose of combating communist influence and actively promoting anti-communist ideas, by fostering relationships with journalists, trade unions and other organizations. In 1956, Conquest left the IRD and became a freelance writer and historian. Some of his books were partly distributed through Praeger Press, a US company which published a number of books at the request of the CIA. In 1962-63, he was literary editor of The Spectator, but resigned when he found it interfered with his historical writing. His first books, Power and Politics in the USSR and Soviet Deportation of Nationalities, were published in 1960. His other early works on the Soviet Union included Soviet Nationalities Policy in Practice, Industrial Workers in the USSR, Justice and the Legal System in the USSR and Agricultural Workers in the USSR.

In addition to his scholarly work, Conquest was a major figure in a prominent literary movement in the UK known as "The Movement", which included Philip Larkin and Kingsley Amis. He also published a science fiction novel and the first of five anthologies of science fiction he co-edited with Amis.

In 1968, Conquest published what became his best-known, The Great Terror: Stalin's Purge of the Thirties, the first comprehensive research of the Great Purge, which took place in the Soviet Union between 1934 and 1939. The book was based mainly on information which had been made public, either officially or by individuals, during the so-called "Khrushchev Thaw" in the period 1956-64. It also drew on accounts by Russian and Ukrainian émigrés and exiles dating back to the 1930s, and on an analysis of official Soviet documents such as the Soviet census.

The most important aspect of the book was that it widened the understanding of the purges beyond the previous narrow focus on the "Moscow trials" of disgraced Communist Party of the Soviet Union leaders such as Nikolai Bukharin and Grigory Zinoviev, who were executed after summary show trials. The question of why these leaders had pleaded guilty and confessed to various crimes at the trials had become a topic of discussion for a number of western writers, and had underlain books such as George Orwell's Nineteen Eighty-Four and Arthur Koestler's Darkness at Noon.

Conquest claimed that the trials and executions of these former Communist leaders were a minor detail of the purges. By his estimates, Stalinist famines and purges had led to the deaths of 20 million people. Other accounts have put the figures higher and lower; for example, according to archival and demographic evidence examined by Alec Nove, there were 10-11 million excess deaths in the 1930s, while according to Norman Davies the number may approach 50 million for the whole Stalin period. In the preface to the 40th anniversary edition of The Great Terror, Conquest states:

"Exact numbers may never be known with complete certainty, but the total of deaths caused by the whole range of Soviet regime's terrors can hardly be lower than some fifteen million."

Conquest criticized western intellectuals for "blindness" with respect to the Soviet Union, and argued that Stalinism was a logical consequence of Marxism-Leninism, rather than an aberration from "true" communism. Conquest did not accept the assertion made by Nikita Khrushchev, and supported by many Western leftists, that Joseph Stalin and his purges were an aberration from the ideals of the "revolution" and were contrary to the principles of Leninism. Conquest argued that Stalinism was a natural consequence of the system established by Vladimir Lenin, although he conceded that the personal character traits of Stalin had brought about the particular horrors of the late 1930s. Neal Ascherson noted: "Everyone by then could agree that Stalin was a very wicked man and a very evil one, but we still wanted to believe in Lenin; and Conquest said that Lenin was just as bad and that Stalin was simply carrying out Lenin's programme."

Conquest accused figures such as Beatrice and Sidney Webb, George Bernard Shaw, Jean-Paul Sartre, Walter Duranty, Sir Bernard Pares, Harold Laski, D. N. Pritt, Theodore Dreiser, Bertold Brecht and Romain Rolland of being apologists for Stalinism.

After the Glastnost era of the 1980s released much information from Soviet archives, Conquest argued the new information supported his arguments. When Conquest's publisher asked him to expand and revise The Great Terror, Conquest is famously said to have suggested the new version of the book be titled I Told You So, You Fucking Fools. (Ultimately, the subtitle A Reassessment was added to a 1990 reprinting). Some critics, however, have argued that examination of archives following the USSR's collapse in 1991 challenges many of Conquest's arguments, such as the duration of sentences, the "political" criteria for prisoners, the ethnic makeup, and the total number of prisoners, which has been revised down to a more realistic number.

In 1986, Conquest published The Harvest of Sorrow: Soviet Collectivisation and the Terror-Famine, dealing with the Holodomor, the famine in Ukraine and elsewhere in the USSR whoe some sources alleged was due to the collectivization of agriculture under Stalin's direction in 1929-31, in which millions of peasants were murdered through starvation, deportation to labor camps and execution.

In this book, Conquest was even more critical of western left-wing intellectuals than he had been in The Great Terror. He accused them of denying the full scale of the famine, attacking their views as "an intellectual and moral disgrace on a massive scale." He later wrote that the western world had been faced with two different stories about the famine in the 1930s, and accused many intellectuals of believing the false one: "Why did an intellectual stratum overwhelmingly choose to believe the false one? None of this can be accounted for in intellectual terms. To accept information about a matter on which totally contradictory evidence exists, and in which investigation of major disputes on the matter is prevented, is not a rational act."

One of Conquest's recent works was Reflections on a Ravaged Century (1999) where he describes the attraction that totalitarian systems of thought seem to hold for many western intellectuals. He traces this attitude back to the Age of Reason and its culmination in the French Revolution.

In 1962, Conquest was divorced from his second wife and, in 1964, he married Caroleen MacFarlane. This marriage was dissolved in 1978 and, in 1979, he married Elizabeth Neece Wingate, a lecturer in English and the daughter of a United States Air Force colonel. In 1981, Conquest moved to California to take up a post at the Hoover Institution at Stanford University.

Conquest is now senior research fellow and scholar-curator of the Russian and Commonwealth of Independent States Collection at the Hoover Institution. He is also an adjunct fellow of the Center for Strategic and International Studies in Washington, D.C., and a former research associate of Harvard University's Ukrainian Research Institute. He is a member of the board of the Institute for European Defence and Strategic Studies. He is a fellow of the British Interplanetary Society and a member of the Society for the Promotion of Roman Studies and the American Association for the Advancement of Slavic Studies.

Conquest has remained a British citizen and, in 1996, he was made a Companion of the Order of St Michael and St George. His other awards and honors include the Richard Weaver Award for Scholarly Letters, the Alexis de Tocqueville Award, and selection by the National Endowment for the Humanities to deliver the 1993 Jefferson Lecture in the Humanities. In 1994 he was elected a Fellow of the British Academy.Conquest is also known as a poet. He has brought out six volumes of poetry and one of literary criticism, edited the seminal New Lines anthologies, and published a verse translation of Aleksandr Solzhenitsyn's Prussian Nights. He received the American Academy of Arts and Letters Award in 1997. He is a fellow of the Royal Society of Literature and the American Academy of Arts and Sciences. He is a frequent contributor to the New York Review of Books, the Times Literary Supplement and other journals.

In November 2005, Conquest was awarded the Presidential Medal of Freedom by George W. Bush. Presidential Medal of Freedom RecipientsIn June 2006, he was awarded the Ukrainian Presidential Medal of Yaroslav the Wise, the highest honor bestowed by Ukraine, in recognition of his scholarship on the Holodomor (the Ukrainian Famine of 1932-1933).

(Dates shown are not necessarily the dates of first publication)

• Common Sense About Russia (1960)
• Power and Politics in the USSR (1960)
• Soviet Deportation of Nationalities (1960)
• Courage of Genius: The Pasternak Affair (1961)
• Industrial Workers in the USSR (1967)
• Soviet Nationalities Policy in Practice (1967)
• Agricultural Workers in the USSR (1968)
• The Soviet Police System (1968)
• Religion in the USSR (1968)
• The Soviet Political System (1968)
• Justice and the Legal System in the USSR (1968)
• Stalin's Purge of the Thirties (1968)
• The Nation Killers: The Soviet Deportation of Nationalities (1970)
• Where Marx Went Wrong (1970)
• Lenin (1972)
• Kolyma: The Arctic Death Camps (1978)
• Inside Stalin's Secret Police: NKVD Politics, 1936-1939 (1985)
• What to Do When the Russians Come: A Survivor's Guide (1985)
• The Harvest of Sorrow: Soviet Collectivization and the Terror-Famine (1986)
• Tyrants and Typewriters: Communiques in the Struggle for Truth (1989)
• Stalin and the Kirov Murder (1989)
• A Reassessment (1990)
• Stalin: Breaker of Nations (1991)
• History, Humanity, and Truth (1993)
• Reflections on a Ravaged Century (1999)
• The Dragons of Expectation. Reality and Delusion in the Course of History., W.W. Norton and Company (2004), ISBN 0-393-05933-2