Uses an artsy technique, considered innovative at the time, first used in "Judgment at Nuremberg" in 1961, where scenes begin in Russian and gradually segue to English, avoiding subtitles or dubbing into English.
John Huston said of this film in his auto-biography 'An Open Book': "I thought 'The Kremlin Letter' had all the makings of a success... The book by Noel Behn had been a best-seller. It had, moreover, all those qualities that were just coming into fashion in 1970 - violence, lurid sex, drugs. The cast was exceptionally strong... and the performances couldn't have been bettered. It was extremely well photographed [by Edward Scaife] - there was a virtuosity, a shine to it. Gladys Hill and I wrote the script, which I considered quite good, though in retrospect it was perhaps overcomplicated."
Source novelist Noel Behn based his novel of 'the Kremlin letter' on his experiences in working for the US Army's Counterintelligence Corps.
This picture was filmed in four countries: Finland, Italy, Mexico, and the USA. The scenes set in Moscow were shot in Helsinki, Finland.
Initially, Steve McQueen was offered the part of Charles Rone, but turned it down. John Huston also considered Warren Beatty and Robert Redford for the part before signing Patrick O'Neal, whom he had strongly considered as a replacement for Montgomery Clift in his earlier film, Reflections in a Golden Eye (1967) prior to his hiring Marlon Brando instead.