It’s well known today that Israeli and U.S. intelligence agencies often cooperate closely, and that Jerusalem routinely provides Washington with important and hard-to-obtain information. Less well known is that this cooperation dates back to the 1950s. It was Israel, for instance, that obtained a copy of Nikita Khrushchev’s 1956 “secret speech” to Communist party leaders, denouncing Stalin. Israel also, on numerous occasions, captured advanced Soviet weaponry from its Arab enemies, which it then gave to the U.S., helping the latter stay abreast of Moscow’s technology and its vulnerabilities. And that’s not all, as Raphael Ofek writes:
During the cold war, U.S. intelligence had difficulty collecting information from behind the Iron Curtain, instead concentrating on technical means of collection, especially aerial photography: first by U-2 planes, then by satellites. Thus, particularly in domains of a clearly technological nature such as the Soviet nuclear threat, it was easy to err through over- or underestimation. [By recruiting retired members of the Soviet defense establishment], the Israeli intelligence community succeeded, in the latter half of the 1970s and the early 1980s, to provide its American counterpart with highly valuable, original information on the Soviet strategic-missile array as it existed at the end of the 1960s.
Based on the information that Israel provided, one could construct a detailed and quite accurate picture of the structure and dispersal of at least some of the Soviet army’s strategic-missile brigades. . . . Some of the intelligence information could be verified with aerial photographs. But it also included details, as well as rumors, that were verified only later. . . .
The CIA expressed its gratitude to the Israeli intelligence community, noting that the information was “unique” and had enabled the agency to adjust its intelligence overestimation on the issue in question. According to a senior CIA official, the information obtained from Israel indicated that Soviet strategic-missile technology was inferior to what the CIA had [previously] believed. . . . [This] Israeli information made a particularly important contribution to America’s ability to defend itself against a Soviet nuclear strike.
Read more on BESA Center: https://besacenter.org/perspectives-papers/israel-intelligence-cold-war/