It is insecurity that beckons deterrence to forestall — under the fear of consequences — any probable infraction by an attacker. Nuclear deterrence also falls in the same ambit and is considered an instrument to strike the balance of power between adversaries. There are three tiers of nuclear deterrence practised by South Asia’s two nuclear powers, India and Pakistan.The first tier is that under the umbrella of nuclear deterrence have grown the adjectives, minimum and credible, one after another, to offer an excuse to both India and Pakistan to initiate and continue their nuclear programmes. The adjective minimum was used after May 1998 and the adjective credible was used after May 1999 by both countries. It is highly probably that, in the future, more such adjectives will join the list to add further ambiguity — read ‘strength’ — to the concept of (nuclear) deterrence. India has been saying that it aims to achieve credible minimum (nuclear) deterrence to counter China’s military prowess whereas Pakistan has been saying that it aims to achieve minimum credible (nuclear) deterrence to counter India’s military competence. In this way, the overwhelming (or asymmetric) conventional war capability of one country is being balanced by a rival weak country through nuclear deterrence, though China is external to South Asia.Having a single nuclear weapon may be considered the lowest border of minimum — even if not minimal — nuclear deterrence to cause corresponding desired minimum destruction but the upper border of the minimum in terms of quantity is not known. The lack of quantification offers numerous chances to both India and Pakistan, which are not recognised nuclear powers yet, to keep on scaling up the number of their nuclear weapons under the ruse of vulnerability of the state. Similarly, having two nuclear weapons may be considered the lowest limit of credible nuclear deterrence to cause corresponding desired minimum destruction but the upper limit of the credible in terms of quantity is not known, though the idea of quality is more embedded in the credible than in the minimum. Nevertheless, subjectivity governs both the minimum and the credible. This is how both the minimum and the credible add a two-fold ambiguity to the concept of nuclear deterrence, and offer a leeway to both India and Pakistan to continue developing and improving nuclear weapons to their contentment. In the case of Pakistan, ambiguity served it to construct a nuclear weapon and ambiguity has been serving it to expand its nuclear inventory.The first nuclear strike may be considered an offence but the second nuclear strike is interpreted as retribution. If the addition of the minimum to the term nuclear deterrence helped both India and Pakistan think of the first nuclear strike against each other, the addition of the credible helped both countries think of the second nuclear strike against each other. The second nuclear strike capability predicates on a country’s survivability to retaliate. This is how the concept of deterrence has been advanced in South Asia to include the capability of the second nuclear strike; the concept of nuclear deterrence has been upgraded to be seen through the lens of the second nuclear strike capability of a country after surviving a nuclear attack.The second tier of nuclear deterrence is that the concept deterrence is being defined in terms of having a nuclear triad by having land, sea and air-based nuclear weapons such as bomber airplanes, Intercontinental Ballistic Missiles (ICBMs) and Submarine Launched Ballistic Missiles (SLBMs). The nuclear triad embodies high-yield Strategic Nuclear Weapons (SNWs) as deterrence and increases the possibilities for the second nuclear strike (after saving a country’s nuclear capabilities) besides enhancing manifold the country’s strategic nuclear deterrence to make massive retaliation possible. Pakistan has distributed its SNWs and has further dispersed their parts to preclude their pre-emptive annihilation. Pakistan’s effort to acquire the nuclear triad is an alternative to its past effort to have strategic depth in the hilly, rugged terrain of Afghanistan. In a way, the presence of strategic depth made the first strike option endearing to Pakistan whereas the presence of the nuclear triad (in the absence of strategic depth) makes the second strike option endearing to Pakistan. The nuclear triad necessitates the existence of a strong, concentrated central command and control mechanism during wartime. Nevertheless, the low-yield Tactical Nuclear Weapons (TNWs) that Pakistan recently claims to have possessed, do not add strength to the nuclear triad but add strength to battlefield maneuvers, when the central command and control mechanism will be diluted (i.e. delegative nuclear control system) to empower the military field commanders to arm and launch these weapons on their volitions on the local or the foreign (attacker’s) land. Pakistan has yet to elaborate on the policy bifurcation on the use of SNWs and TNWs in the face of a crisis-prone and crisis-ridden South Asia.The third tier of nuclear deterrence is that both India and Pakistan have kept open the option of first use of a nuclear strike against each other. Pakistan had already kept that option open but India did so in October 2010 when its National Security Advisor (NSA) Shri Shivshankar Menon, said in a speech at the National Defence College, New Delhi, that India was practising “no first use against non-nuclear weapon states”. Perceptibly, this development nudged Pakistan to envisage and acquire the nuclear triad as soon as possible.To sum up, the cycle of nuclear deterrence is continuing and so is the nuclear arms’ race in South Asia. Moreover, powers external to the region are also responsible for triggering the nuclear arms race in South Asia and this is how a part of the problem or solution lies external to the region. Additionally, the ad hoc concept of deterrence to establish peace has become permanent. Furthermore, Pakistan has to realise that it is important to introduce transparency into and draw the boundaries of its nuclear (weapons) programme before the programme becomes counterproductive. The writer is a freelance columnist and can be reached at qaisarrashid@yahoo.com