The Great Terror is a book by British writer Robert Conquest, published in 1968. It gave rise to an alternate title of the period in Soviet history known as the Great Purge. The complete title of the book is The Great Terror: Stalin's Purge of the Thirties. A revised version of the book, called The Great Terror: A Reassessment, was printed in 1990 after Conquest was able to amend the text, having consulted recently opened Soviet archives.
One of the first books by a Western writer to discuss the Great Purge in the Soviet Union, it was based mainly on information which had been made public, either officially or by individuals, during the Khrushchev Thaw in the period 1956-1964. It also drew on accounts by Russian and Ukrainian émigrés and exiles dating back to the 1930s. Lastly it was based on an analysis of official Soviet documents such as the census. - Wikipedia