A GRU colonel, Penkovsky had served under military attaché cover in Ankara, Turkey, in 1955, but upon his return to Moscow volunteered his services to the Americans and Canadians as a source of intelligence. He was at first rebuffed as a likely provocation, but was taken seriously after a further approach to the Secret Intelligence Service in December, through a British businessman, Greville Wynne. This resulted in a joint SIS–Central Intelligence Agency operation that lasted 18 months, until his arrest by the KGB in October 1962, code-named HERO by the CIA and YOGA by SIS.
During 1961 Penkovsky made three visits abroad, to London in April and July 1961 and to Paris, and on each occasion he underwent a lengthy debriefing by a CIA team led by Joe Bulik and Kisevalter, and two SIS officers, Michael Stokes and Harold Shergold.
Penkovsky’s information, distributed in London and Washington, D.C., under the code names ARNIKA, RUPEE, and IRONBARK, included details of his GRU colleagues, planned operations, and the deployment of Soviet intercontinental ballistic missiles.
Convicted at a public trial in May 1963, Penkovsky was executed, and Greville Wynne was imprisoned and later exchanged in a spyswap.