The Soviet Union cast a crucial UN vote in favor of the creation of a Jewish state in 1947. Then it very quickly turned against Israel, as Shammai Siskind explains:
[A]nti-Zionist sentiment had been brewing within the Soviet leadership well before the emergence of Israel. Vladimir Lenin himself allegedly saw the Zionist project as a form of bourgeois colonialism. . . . By the early 1950s, however, having realized that Israel would not become a Soviet-type socialist state, and recognizing the Arab states’ far greater geostrategic, geopolitical, and economic importance, Moscow took an increasingly anti-Israel line. Soviet support for the Arabs moved from the diplomatic to the material in 1955 when Moscow signed a large-scale arms deal with Egypt (via Czechoslovakia) that included heavy-weapons platforms.
Jerusalem in turn gravitated toward Washington as the cold war took shape. Since Israel faced Soviet weapons in its wars with Egypt and Syria, it shared a common interest with Washington in gathering intelligence on the latest technology. Israeli efforts led to some stunning coups, such as Operation Diamond, in which it acquired a Soviet-made MiG-21 fighter jet, at the time one of the most sophisticated aircraft in the world. Siskind writes:
In 1963, Israeli agents in Tehran learned of an Iraqi fighter pilot, Munir Redfa, who was considering leaving Iraq after years of discrimination within the military due to his Christian roots. A Mossad agent contacted him, and after building a relationship, convinced him to meet with more senior officials.
In a meeting with government agents in Israel, Redfa agreed to fly his MiG to Israel in return for $1 million in payment plus the smuggling of his family out of Iraq. Within a few weeks after his arrival in Israel, Israeli Air Force pilots used his aircraft in a number of test flights. They analyzed the jet’s strengths and weaknesses and flew it against their own fighters. They mastered the aircraft, marveling at its speed and maneuverability. This proved invaluable during the June 1967 Six-Day War, when Egypt and Syria were both armed with MiGs.
A month later, Israeli authorities loaned the MiG to their U.S. counterparts, who were able to evaluate the plane themselves under the “Have Donut” program. . . . U.S. personnel also had a chance to peruse the training and tactical manuals delivered by Redfa, which no doubt substantially aided U.S. efforts to counter Soviet air power. The transfer of the MiG-21 was a major boost in U.S.-Israel defense relations.
Israel also delivered to the CIA the “secret speech” by Nikita Khrushchev in which the Soviet premier denounced Stalin’s crimes, and later obtained crucial documents about the USSR’s missile technology.