India possesses a smaller number of nuclear weapons, estimated in 2015 to range between ninety and 120. However, New Delhi recently acquired a full nuclear triad of air-, land- and sea-based nuclear platforms when it deployed its first home-produced nuclear-powered submarine, the INS Arihant. The Arihant is capable of launching a dozen K-15 Sagarika submarine-launched ballistic missiles. However, these are limited to a range of 750 kilometers, and are thus incapable of reaching the major inland cities of Pakistan or China, a shortcoming India is attempting to address with new K-4 missiles, derived form the land-based Agni-III. New Delhi intends to produce three more nuclear submarines over the years, while Pakistan is considering building one of their own.
While the United States is preoccupied by the threat of nuclear weapons in the hands of potential adversaries such as Russia, China or North Korea, the danger of nuclear conflict may actually be greatest between two of its allies, Pakistan and India. The two nations have engaged in four wars starting since their partition along religious lines in 1947. A fifth could be drastically more costly, as their nuclear capabilities continue to grow and diversify.
Several years ago I made the acquaintance of a Pakistani nuclear science student in China. Curious about the thinking behind his country’s nuclear program, I asked if he really believed there was a possibility that India would invade Pakistan. “There’s still a lot of old-school thinkers in the Congress Party that believe India and Pakistan should be united,” he told me.
I doubt there are many observers outside of Pakistan who believe India is plotting to invade and occupy the Muslim state, but a feeling of existential enmity persists. The third conflict between the two countries in 1971 established India’s superiority in conventional warfare—not unexpectedly, as India has several times Pakistan’s population.
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The bone of contention has always been the Indian state of Jammu and Kashmir. At the time of partition, the predominantly Muslim state was politically divided over which nation to join. When Pakistani-allied tribesmen attempted to force the issue, the Hindu maharaja of the region chose to accede to India, leading to the first war between India and Pakistan. Ever since, the line of control between the Indian and Pakistan side has remained bitterly contested, with artillery and sniper fire routinely exchanged. Pakistan intelligence services have infiltrated insurgents and plotted attacks across the border for decades, and Indian security troops have been implicated in human-rights violations and killings of the locals as a result of their counterinsurgency operations.
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Pakistan does have to fear the potential of an Indian counterstrike intended to retaliate for a terrorist attack by Pakistani-aligned groups, such as the killing of 166 in Mumbai by Lashkar-e-Taiba in 2008 or the attack on Indian parliament in 2001 by Jaish-e-Muhammad. In both cases, the attackers had ties with Pakistani Inter-Services Intelligence, and Islamabad has shown limited willingness or ability to crack down on these groups. Complicating matters, civilian control of the military is far from consolidated in Pakistan, and it would be quite possible for ISI or some other agency to carry out such activities on its own initiative without the knowledge or support of the head of state.
India’s military has formulated a “Cold Start” doctrine to enable its forward-deployed land forces to launch an armored assault into Pakistani territory on short notice in response to a perceived provocation from Islamabad. This new strategy was devised after the Indian Army’s armored strike corps took three weeks to deploy to the border after the attack on the Indian parliament in 2001, by which time Pakistan had already mobilized its own troops.
Islamabad sees nuclear weapons as its deterrent against a conventional attack, and Cold Start in particular. This is demonstrated by its refusal to adhere to a “No First Use” policy. Pakistan has an extensive plutonium production capacity, and is estimated to possess 130 to 140 warheads, a total that may easily increase to 220 to 250 in a decade, according to a report by the Bulletin of Atomic Scientists.
Many of the new weapons are smaller, short-range tactical weapons intended for targeting frontline troops. To enable a second-strike capability, Pakistan has also empowered local commanders to launch retaliatory nuclear strikes in case the chain of command is disrupted.
While battlefield nuclear weapons are less likely to cause the mass civilian casualties that a strike against a densely populated city would produce, they are deeply worrying in their own way: a state may be more tempted to employ tactical nuclear weapons, and perceive doing so as being intrinsically less risky. However, many simulations of nuclear war suggest that tactical-nuclear-weapon usage rapidly escalates to strategic weapons .