Asia Defense

Are Pakistan’s Battlefield Nuclear Weapons a Mirage?

What exactly is behind Pakistan’s much-discussed low-yield Nasr? And how might it be used?

By Aditya Ramanathan and Kunaal Kini for
Are Pakistan’s Battlefield Nuclear Weapons a Mirage?
Credit: Inter Services Public Relations (ISPR)

In April 2011, Pakistan conducted the first test of its short-range Hatf-IX or Nasr rocket. The test was interpreted as marking a shift in Pakistan’s nuclear posture to “full spectrum deterrence,” which envisages a complete range of “strategic, operational and tactical” nuclear weapons that would give India “no place to hide.” More specifically, Pakistan claimed the Nasr was intended to “pour cold water over Cold Start,” the name given to the Indian Army’s doctrine, which involves the rapid mobilization of division-sized integrated battle groups making shallow incursions into Pakistani territory.

Although Cold Start is still a work-in-progress, and Pakistan already enjoys considerable conventional deterrence against India, its army has tested the Nasr several times since 2011, publicly talking up its  “shoot and scoot attributes” that supposedly help “deter evolving threats.” Despite the many tests, it’s not clear if the rocket system is actually in service, since it apparently remained undeployed as late as 2016.

Understanding the Nasr

The first Nasr test came seven years after the new Cold Start doctrine was revealed at an Indian Army Commander’s Conference in 2004.In the years that followed, the Indian Army leadership remained cagey about discussing the new doctrine, only obliquely referring to a “proactive strategy.” That changed in 2017, when current army chief General Bipin Rawat bluntly acknowledged its existence.

The Nasr is generally believed to be based on either China’s WS-2 Weishi or the similar AR1A/A100-E conventional rocket artillery system. According to the one estimate from a trio of scholars from Bangalore’s NIAS, the Nasr’s warhead section is 1.6 meters long, with a cylindrical portion that’s just under a meter in length and a conical portion that adds another 660 mm. The outer diameter of the cylindrical portion is 361 mm. The Nasr is believed to have a payload capability of 400 kilograms. While the rocket itself is unremarkable, designing and manufacturing a nuclear warhead for such a small weapon system presents its own hurdles.

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Design Challenges

The simplest way for Pakistan to design an ultra-compact warhead on the Nasr would be to obtain a design from someone else. China would be the most probable candidate. While such a transfer can’t be ruled out, it’s still unlikely the Chinese could have provided Pakistan with an off-the-shelf design. The People’s Liberation Army has no known nuclear-capable missiles with a similar range or payload. Indeed, China has a no-first-use policy that eschews battlefield nuclear weapons.

However, Pakistan is known to have received the Chinese CHIC-4 bomb design, which was first tested in 1966. China may have even subsequently tested a Pakistani variant in 1990. The CHIC-4 is a bulky design that reputedly weighs 1,180 kilograms. According to Brigadier Feroz Hassan Khan, a chronicler of Pakistan’s nuclear weapons program, Pakistan cut the weight of the CHIC-4 design down to about 500 kilograms.

According to Khan, the nuclear test conducted in the Kharan Desert on May 30, 1998, was of a “miniaturized device” for ballistic missiles and aircraft. His claim gains some credence from events a decade later, when investigators following the A.Q. Khan network in Switzerland found bomb plans that were either identical or similar to that of the 1998 device. A story in the New York Times described the device as being “half the size and twice the power” of the CHIC-4 and featuring “far more modern electronics.”

Khan also goes on to claim that Pakistani nuclear scientists later halved the weight of the nuclear device again bringing it down to 220 kilograms. However, it’s not clear when this was achieved or how much they managed to reduce the weapon’s volume.  What seems likely is that Pakistan possessed viable warhead designs for its medium-range ballistic missiles by 1998, even if these warheads were too large for the Nasr.

Plutonium or Uranium?

Like China, Pakistan started out by making implosion bombs based on highly enriched uranium (HEU). (In these bombs, a conventional explosive compresses the fissile core into a supercritical mass.) Pakistan’s 1998 nuclear tests were based on such designs. But for smaller warheads like the Nasr’s, Khan believes Pakistani scientists will “likely use a plutonium warhead with an implosion assembly.” The NIAS study similarly concludes that a variant – the plutonium-based linear implosion device – is best suited for the slim profile of the Nasr missile.

However, as the authors of the NIAS study note, there are two problems with this approach. First, since the linear variant needs twice the amount of fissile material as a spherical implosion system, Pakistan would run out of its estimated plutonium stock (as of 2013) after producing just 12 warheads. Second, any such device would be untested.

An alternative for Pakistan is to reject the implosion system altogether and produce a simple gun-type HEU device – essentially a highly miniaturized version of the bomb dropped on Hiroshima in 1945. Such a device would need no testing and could be fitted into the Nasr. It would, however, go against the deeply-ingrained preference for implosion devices among Pakistan’s weapon-makers.

Whatever its design options, Pakistan may also be facing greater constraints on its supply of fissile material than previously thought. While previous estimates put Pakistan’s arsenal size in 2018 at 140-150 warheads (and growing at the rate of about 10 warheads a year), a recent assessment suggests Pakistan’s dwindling domestic supply of uranium will limit its nuclear arsenal size to between 112 and 156 weapons. While such studies are necessarily speculative, it’s likely Pakistan will be forced to make hard choices when it allocates weapons-grade material among its growing array of missiles.

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Considering the Cold War Experience

Pakistan could adopt more than one pathway toward miniaturizing a Nasr warhead, but how long would the process take? Information about the current state of Pakistan’s nuclear weapons program is scarce, but U.S. and Soviet efforts at miniaturization during the early years of the Cold War provide some indications.

In 1949, the United States began a project to develop nuclear artillery for battlefield use. Just four years later, a 280 mm cannon fired a shell with the new W-9 warhead, which airburst 10 kilometres away, with a yield of about 15 kilotons. The W-9 was a simple gun-type HEU fission device. Over the next decade, the United States would produce even smaller nuclear artillery, including a tiny plutonium linear implosion warhead that could be fired from a standard 155 mm artillery piece.

The Soviets took longer to miniaturize. After they became a nuclear power in 1949, the Soviets struggled to catch up with the U.S. atomic artillery program, only producing small warheads in the early 1960s. By then, new nuclear-capable artillery rockets like the Luna-M had already superseded atomic cannons.

Considering these time scales of 4-15 years, could Pakistan have developed a miniaturized device for the Nasr between the first indications of Cold Start in 2004 and the present?

In developing a miniaturized warhead, the Pakistanis would have enjoyed two principal advantages over their Cold War counterparts. One, they would have had a head start, having worked on warhead designs since the 1970s. Khan notes that between 1983 and 1995, Pakistan carried out at least 24 “cold tests” of their nuclear devices (in which the bomb is detonated minus the fissile core). The devices were also ruggedized and tested for “vibrations, environment, acceleration,” according to a senior Pakistani nuclear physicist, Samar Mubarakmand quoted by Khan. In May 1995, Pakistan conducted a successful aerial cold test from a combat aircraft, with the device exploding 500 meters above ground.

The second advantage the Pakistanis would have over older Soviet or American nuclear weapons designers is advances in technology. For instance, modern electronics would make it easier to design reliable fuses and to correctly detonate the weapon’s explosive lenses.

Against these, Pakistan suffers three disadvantages. One, for all its diversion of resources, Pakistan cannot match the budgets of the superpowers at the height of the Cold War. Two, the Soviet and American programs were enabled by an abundance of fissile material. In contrast, Pakistani supplies are constrained. Three, the superpowers could conduct hot tests, allowing them to validate and improve their designs. Pakistan, on the other hand, can’t perform hot tests of its new warhead designs without incurring widespread diplomatic wrath.

A Limited and Vulnerable Arsenal

This article assumes Pakistan’s nuclear weapon-makers are adequately competent and get preferential access to resources. Nevertheless, to make Nasr warheads, they would not only have to manage costs but also work with a limited supply of fissile material and design new nuclear warheads without being able to test them. It is conceivable Pakistan has skipped these painful steps entirely and is simply bluffing about the Nasr’s nuclear capabilities. Lacking certainty, India would still have to factor in nuclear-capable Nasrs in its plans, even if it remains Pakistan would actually use the rocket.

Another approach for Pakistan would be to produce only a small number of nuclear warheads for the Nasr while increasing the number of conventionally armed Nasr rockets and launchers in its inventory. During a crisis, Pakistan could conspicuously move a few launchers to catalyze intervention from third-parties worried about nuclear escalation. If crisis turns into conflict, the Pakistan Army would hope that a multitude of mostly conventional Nasr launchers on the move would stress Indian intelligence, surveillance, reconnaissance (ISR) resources and divert its military efforts. In Pakistan’s calculation, this would have the effect of complicating India’s plans while minimizing its own command and control challenges.

However, this will not solve the problems inherent in a system like the Nasr. The rocket’s short range of 70 kilometers would force the Pakistan Army to deploy launchers perilously close to the fighting, making them vulnerable to India’s conventional firepower. This makes the Nasr highly destabilizing since the Pakistanis will have to worry about survivability of what is likely to be a small arsenal of nuclear-capable rockets.

Targeting Indian forces will also remain a challenge. Once a decision has been made to use nuclear-tipped Nasrs, the Pakistan Army would have to locate mobile targets, ensure there are no friendly forces in the vicinity, and then quickly communicate that information to the rocket crews before they are destroyed and before the information becomes obsolete. What’s more, it will have to do all this while immersed in the thick fog of war.

The technical and operational hurdles involved in creating a fully-functional force of battlefield nuclear weapons would challenge any country. For Pakistan, some of these challenges – such as limits on fissile material and the short range of the Nasr – are especially acute. There are suggestions the Nasr would be used as part of a larger nuclear first strike against both counterforce and countervalue targets. But Pakistan has a formidable arsenal of missiles that offer better strike options than the Nasr. All things considered, it is likely the Nasr is at present a mirage aimed at the minds of India’s decision makers, rather than a military reality targeted at its armoured columns.

Aditya Ramanathan is a policy researcher with the Takshashila Institution. Kunaal Kini is an intern with the Takshashila Institution.