The Soviets did not need to ‘steal’ or ‘get’ any Tomcats: obtaining quite good intel on the F-14—from the USA—proved quite easy for the KGB. A few words ‘on popular request.’
What’s false is the claim that any Iranian F-14 was ever ‘given’ to the Soviets. The Soviets never manufactured parts for TF-30 engines of Iranian F-14s, nor did they develop the Zaslon radar or the R-33 missile for their MiG-31 based on any kind of intelligence from Iran. It’s a fact that the Soviets were never left even anywhere close to any of the Iranian F-14s.
Regardless of which Western sources have released any of such rumors, all are incorrect. What is also fake are all the photos purportedly ‘showing ex-Iranian F-14s undergoing testing (“against MiG-25s”) in the USSR.’
(What actually happened, if anything, was that details of the MiG-31, Zaslon, and the R-33 were revealed to the CIA—and then by Adolf Tolkachev, one of the chief designers at what is nowadays Vympel Institute—and that already in 1979, i.e., before the MiG-31 entered operational service in the USSR.)
The Soviets did not need to ‘steal’ or ‘get’ any Tomcats: obtaining quite good intel on the F-14, from the USA—proved quite easy for the KGB. Perhaps ironically, the rest came from diverse books. Gauging by specific illustrations in Soviet internal publications, they did make extensive use of Mike Spick’s ‘Modern Combat Aircraft: F-14’ (Salamander, London, 1983).
Already in the same year, the Soviet air force published a related booklet, ‘Naval Fighter F-14 (US’ Navy)’—see the attached scan. BTW, this was ‘nothing special.’
They’ve had such ‘tactical manuals’ for all other major types of Western aircraft, too—including F-4s, F-15s, F-16s, F-111s, E-2C, E-3A, even for the F-117A and the B-2A: arguably, only top-ranking fighter pilots were getting these to see (the reason for this was the ‘complex’ training system for all their pilots), which is why they remain relatively unknown outside specific circles.
More interesting F-14 stories written by Tom Cooper are featured in Helion & Company In the Claws of the Tomcat.