By Brig Gurmeet Kanwal (Retd). (DefenceIndia Special)

One of the contentious issues that had threatened to derail the historic nuclear agreement signed by India and the US is the number of nuclear warheads that India needs for credible minimum deterrence.

While the estimates put forward by Indian analysts range from one to two dozen 'survivable' warheads at the lower end of the spectrum to over 400 warheads, these are mainly based on gut judgments and not on cold logic.

Nuclear weapons are political weapons and not weapons of 'fighting'. Their sole purpose is to deter the use and threat of use of nuclear weapons. A nation's nuclear force structure depends on its nuclear doctrine and deterrence philosophy.

The number of nuclear warheads that a nation must stockpile depends on availability and quality of weapons-grade fissile material, its mastery of nuclear weapons design technology, the accuracy and reliability of its delivery systems, the fiscal constraints that govern its defence budget, the present and future air and missile defence capability of its adversaries, and their ability to absorb retaliatory nuclear strikes.

If deterrence fails, in keeping with its nuclear doctrine, India will have to absorb a nuclear strike before retaliating against the adversary's major cities and industrial centres.

India's targeting philosophy is based on a 'counter value' (as against 'counter force') strategy of massive punitive retaliation to inflict unacceptable damage to the adversary's major population and industrial centres.

A retaliatory strike capability to destroy eight to 10 major population and industrial centres would be adequate to meet the requirements of deterrence.

For 10 counter value targets to be destroyed in the adversary country, a total of 40 nuclear warheads, at four warheads of 20 to 40 kiloton each per target, would be adequate to cause unacceptable damage in a retaliatory nuclear strike.

This is possible if the probable error of the Agni IRBM delivery systems is taken to be 1,000 metres and a destruction assurance level of 0.7 (about 70 per cent) is considered acceptable.

If the efficiency or overall reliability of India's nuclear delivery system is taken to be between 0.5 and 0.6 (50 to 60 per cent), a reasonable assumption for a modern nuclear force, then 75 warheads must actually be launched for about 40 to 45 warheads to explode successfully over their targets as some missiles may fail to take off, some may veer off course, some may be intercepted and some warheads may either fail to explode or may explode in a sub-optimal manner.

Hence, a minimum of 75 warheads and, of course, their delivery systems must survive the enemy's first strike on Indian targets and be available for retaliation.

Despite the best possible concealment and dispersion measures, approximately 50 per cent of the nuclear warheads and delivery systems may be destroyed in a first strike by the adversary.

It would, therefore, be reasonable to plan a warhead stocking level of at least twice the number of warheads that are actually required to be launched, that is, 150 warheads.

The last aspect to be catered for is a prudent level of reserves for larger than anticipated damage to own nuclear forces in a first strike and for unforeseen eventualities.

Escalation control and war termination strategies would also be dependent on the ability to launch counter-recovery strikes and some fresh strikes. One-third the required number of warheads should be adequate as reserves.

Hence, the total requirement works out to 200 nuclear warheads for a minimum deterrence doctrine with a no-first-use strategy if 10 major population and industrial centres are to be attacked in a retaliatory strike to achieve a 70 to 80 per cent assurance level of destruction.

The safeguard restrictions that India has voluntarily accepted under the agreement with the US and the number of nuclear reactors that it has decided to keep in the military list will ensure that India has adequate fissile material to manufacture 200 plus nuclear warheads.

Treaty obligations will not compromise India's sovereign right to take all steps necessary to assemble a larger number of warheads if needed in future. It is time to let this issue rest and move on.

(The writer is director, Security Studies, Observer Research Foundation, New Delhi)

(Reproduced with Permission from the Author)