A modern ICBM is able to deliver payloads to multiple targets at the same time. The technology is called MIRV [1], and U.S. has had it since the early 70s.
Since a space shuttle has a much larger payload than an ICBM and is also much more maneuverable, the Soviets probably couldn't exclude the possibility that it can deliver enough payloads to wipe off several cities and/or military bases in a single pass. They were already having trouble developing effective countermeasures to MIRV; a shuttle would have been a nightmare.
Since a space shuttle has a much larger payload than an ICBM and is also much more maneuverable, the Soviets probably couldn't exclude the possibility that it can deliver enough payloads to wipe off several cities and/or military bases in a single pass. They were already having trouble developing effective countermeasures to MIRV; a shuttle would have been a nightmare.
[1] https://en.wikipedia.org/wiki/Multiple_independently_targeta...