How did improved missile guidance systems increase fears of a first strike?

Improved missile guidance systems increased fears of a first strike by enabling unprecedented accuracy, which fundamentally challenged the stability of nuclear deterrence.1

In the context of nuclear strategy, early ballistic missiles lacked the precision to reliably destroy hardened military targets like missile silos. However, as guidance technology advanced—characterized by lower circular error of probability (CEP) and the integration of sophisticated systems like stellar and satellite navigation—missiles became capable of striking specific military installations with high precision.23

This technological leap created a "window of vulnerability" for land-based intercontinental ballistic missiles (ICBMs). Critics argued that an adversary could potentially launch a preemptive first strike against an opponent's missile force, destroying a significant portion of their retaliatory capability while limiting collateral damage. Because these improved systems made it theoretically possible to disarm an opponent's land-based deterrent, they fueled concerns that a nation might be tempted to strike first to gain a decisive military advantage, rather than relying on the traditional, more stable doctrine of mutual assured destruction.14