It can be argued that except under the most extreme provocation we would shrink from any retaliatory strike that had no significant chance of eliminating or softening the Russian return strike. According to this argument, a pair of invulnerable SAC’s is a pair of neutralized SAC’s; and while that might be the best kind in a completely bi-polar world, it is a luxury that we could not afford in the existing world—a world in which there is a large “third area” in which we wish to deter Russian aggression by a threat more credible than that of mutual suicide.

XREF: This anticipates the concept of mutual assured destruction (MAD) and how a second-strike capability undermines credibility of retaliation — echoes of deterrence theory debates.

Thomas C. Schelling, The Strategy of Conflict, loc. 582