Nuclear deterrence is not a function of the exchange ratio of the damages inflicted by both sides. The crux of nuclear deterrence is survival of the retaliatory force and the adequacy of the survived force to inflict unacceptable punishment.
As the man who drafted the nuclear doctrine, the late K Subrahmanyam explained: “In India’s case, it would mean that the ability of the country to retaliate against a nuclear attack on it by either of its two nuclear neighbours, should be credible to the potential adversary. In other words, the retaliation should result in unacceptable damage in terms of population and property. So long as India has a survivable retaliatory force, the punishment is certain.”