Although the numerical composition of the Soviet force was well known to U.S. intelligence, the capabilities of the deployed missiles were much harder to assess. Gradually, the question of the counterforce potential of the new force became increasingly contentious among U.S. analysts. Different assumptions about the accuracy of the Soviet missiles and therefore their ability to attack hardened targets, or about the ability of Soviet silos to withstand a U.S. attack, led to dramatically different conclusions about the intent of the Soviet military buildup.
When the Soviet Union began deploying its first MIRVed ballistic missiles in 1974, the consensus of the U.S. intelligence community was that the accuracy of these missiles, though better than those deployed in the 1960s, was no greater than about 0.25 nautical miles (470 meters) circular error probable (CEP). At that time, the U.S. intelligence community estimated that the Soviet Union could improve the accuracy of its next generation of missiles, to be deployed in the early 1980s, to 0.15 nautical miles (280 meters).
These estimates meant that the Soviet Union did not have a significant counterforce capability and likely would not achieve one until the mid-to-late 1980s.
This consensus was challenged by the Team B panel, which had been charged with evaluating the Soviet missiles’ accuracy as part of its mandate. Although the U.S. intelligence community initially contested the conclusions of the panel, National Intelligence Estimates (NIEs) issued after 1976 generally assumed a higher level of accuracy (about 400 meters) for the first-generation of Soviet MIRVed missiles.
The revised estimate of the missiles’ accuracy from 470 meters to 400 meters was not a significant change in itself, for it did not fundamentally alter the estimate of the counterforce capability of the Soviet ICBM force. Combined with other developments, however, this revision proved highly consequential.
One development was the apparent change in the timeline of the Soviet missile modernization program. In October 1977 the Soviet Union began flight tests of the modified versions of its SS-18, SS-19, and SS-17 missiles with “improved tactical-technical characteristics.” These versions were known as the R-36MUTTH, the UR-100NUTTH, and the MR UR-100UTTH, respectively.
The U.S. intelligence community apparently considered these to be modernized versions of missiles that were not expected to arrive until the early-to-mid-1980s. Accordingly, U.S. intelligence estimated that the “UTTH” missiles had achieved a level of accuracy of 0.12–0.15 nautical miles (220–280 meters).
Improved accuracy was indeed a main goal of the “UTTH” modernization program. According to Russian sources, most of the improvements were concentrated on the post-boost vehicle and the missile guidance system. Missile frames were almost unaffected, although the number of warheads carried by the R-36MUTTH missile increased from 8 to 10.
The Soviet modernization program did result in improved missile accuracy, but it remained significantly lower than in U.S. estimates. Figure 1 shows the results of flight tests of the MR UR-100UTTH missile, which indicate that the CEP, demonstrated in the test series, was about 400 meters. The R-36MUTTH and UR-100NUTTH missiles demonstrated similar performances.
Based on the results of these tests, Soviet military planners estimated that the accuracy of the “UTTH” missiles was 350–400 meters. These values, as well as the accuracies of other Soviet ICBMs, are presented in Table 2, along with data on the yield of the missiles’ warheads.
As the data indicate, the U.S. estimates significantly overestimated the accuracy that Soviet missiles were able to demonstrate in the late 1970s and early 1980s. The Soviet Union did indeed develop missiles with accuracies as high as 220 meters, but these missiles—the R-36M2 (SS-18 Mod 5) and the RT-23UTTH (SS-24)—were not deployed until 1988. In fact, the Soviet Union had not made the decision to proceed with the development of these two missiles until 1983.
U.S. estimates of the accuracy of the Soviet missiles had a direct effect on the projections of the counterforce potential of the Soviet ICBM force. Figure 2 shows projections made by the U.S. intelligence community in 1978 and 1979 of the number of Minuteman silos that could survive a two-on-one Soviet attack.
These estimates remained largely unchanged in the early 1980s; for example, in 1981 an NIE reported that “in a well-executed strike Soviet ICBMs would have the potential—using two RVs [reentry vehicles] against a Minuteman silo—to achieve a damage expectancy of about 75 to 80 percent today, and about 90 percent by the mid-1980s.”
Figure 2 offers a comparison of these estimates, with the estimate of the missiles’ actual capability that takes into account the data on accuracies and yields presented in table 2, as well as the actual composition of the Soviet ICBM force.
As Figure 2 demonstrates, only in 1991 did the Soviet Union barely reach the counterforce capability that the U.S. intelligence community reported it had achieved a decade earlier.