The main U.S. Cold War strategy was to turn China against the USSR. Every Russian-made SAM transferred to North Vietnam through China added incrementally to the seriousness of the Sino-Soviet rift. In 1965, the USSR sent North Vietnam 80 million dollars-worth of SAMs and launchers, or about 60% of the $142,000,000 million in Soviet military aid. On 16 February 1966, it was reported that North Vietnam had a total of 84 SAM sites, which was an increase of 21 sites during recent weeks. But this report concluded: “In terms of actual threat, the expansion of prepared firing positions does not increase DRV capabilities to deter US air operations.” A later estimate put it closer to 130 SAM sites. Coincidentally, American bomber runs sought to soak up the maximum number of SAMs, since having to import new ones through China dramatically increased Sino-Soviet tensions.

The surface-to-air missiles provided by the USSR posed a huge threat to American planes. But as of 17 August 1966, only 26 planes had been shot down by SAMs, as compared to 272 brought down by AA fire: “Surface-to-Air missile defenses have played a significant role in inflicting losses, not by direct effects, but by forcing attack aircraft down into the range of anti-aircraft guns.” Still, the 384 lost aircraft out of 100,784 sorties equalled only 0.3%, “which has been somewhat less than predicted.” A secret American goal was to increase dramatically the number of SAMs the USSR shipped to North Vietnam through China. While only 200 SAMs were provided in 1965, and 1,100 in 1966, in just the first six months of 1967 alone an estimated 1,750 SAMs were sent to North Vietnam, valued at $52 million, one of the single largest components of the $220 million in Soviet aid. A major U.S. goal was to put additional pressure on this supply line. As Walt Rostow told LBJ on 11 February 1967, “the trouble in China may affect supplies to Hanoi,” which makes it “clear the Chinese are trying to force a break in relations with Moscow” (see Map 8).