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Pakistani nuclear forces
Hans M. Kristensen,
Robert S. Norris &
Julia Diamond
Published online: 31 Aug 2018
Pakistan continues to expand its nuclear arsenal with more warheads, more delivery systems, and a growing fissile materials production industry. Analysis of a large number of commercial satellite images of Pakistani army garrisons and air force bases shows what appear to be mobile launchers and underground facilities that might be related to nuclear forces.
Table 1. Pakistani nuclear forces, 2018.
We estimate that Pakistan now has a nuclear weapons stockpile of 140 to 150 warheads.
With several delivery systems in development, four plutonium production reactors, and its uranium enrichment facilities expanding, however, Pakistan has a stockpile that will likely increase further over the next 10 years. The size of the increase will depend on many factors. Two key factors will be how many nuclear-capable launchers Pakistan plans to deploy, and how much the Indian nuclear arsenal grows. Speculation that Pakistan may become the world’s third-largest nuclear weapon state – with a stockpile of some 350 warheads a decade from now – are, we believe, exaggerated, not least because that would require a buildup two to three times faster than the growth rate over the past two decades. We estimate that the country’s stockpile could more realistically grow to 220 to 250 warheads by 2025, if the current trend continues. If that happens, it would make Pakistan the world’s fifth-largest nuclear weapon state. But unless India significantly expands its arsenal or further builds up its conventional forces, it seems reasonable to expect that Pakistan’s nuclear arsenal will not continue to grow indefinitely but might begin to level off as its current weapons programs are completed.
Nuclear policy developments
Pakistan is modifying its nuclear posture with new short-range nuclear-capable weapon systems to counter military threats below the strategic level. The efforts seek to create a full-spectrum deterrent that is designed not only to respond to nuclear attacks, but also to counter an Indian conventional incursion onto Pakistani territory.1 This development has created considerable concern in other countries, including the United States, which fears that it lowers the threshold for nuclear use in a military conflict with India.
In the Worldwide Threat Assessment for 2018, US Director of National Intelligence Daniel R. Coats said, “Pakistan continues to produce nuclear weapons and develop new types of nuclear weapons, including short-range tactical weapons, sea-based cruise missiles, air-launched cruise missiles, and longer-range ballistic missiles. These new types of nuclear weapons will introduce new risks for escalation dynamics and security in the region” (Coats 2018).
Pakistan’s National Command Authority, which includes all government agencies involved in the nuclear mission, held its 23rd meeting on 21 December 2017, under the chairmanship of then-Prime Minister Shahid Khaqan Abbasi. The group reviewed a study of “certain destabilizing actions” occurring in the region around Pakistan, including “the massive arms build-up in the conventional domain, nuclearization of the Indian Ocean Region and plans for development/deployment of [ballistic missile defense].” The National Command Authority had paid similar attention to conventional weapons development at its meeting in 2016.
At the 2017 meeting, according to a Pakistani Inter Services Public Relations press release, the command authority “reiterated Pakistan’s policy of developing and maintaining Full Spectrum Deterrence, in line with the policy of Credible Minimum Deterrence and avoidance of arms race,” while expressing confidence in the country’s “capability to address any form of aggression” (ISPR 2017d). The National Command Authority also reviewed the “Nuclear Security Regime” of the nuclear arsenal and expressed “full confidence” in both Pakistan’s command and control systems and existing security measures meant to “ensure comprehensive stewardship and security of strategic assets and materials.” It lauded the nuclear arsenal’s “high standards of training and operational readiness.”
The December 2017 meeting emphasized that Pakistan strives for “peaceful coexistence in [South Asia] and will endeavor to work with its neighbors to ensure strategic stability” there (ISPR 2017d). As in 2016, the National Command Authority’s latest statement on security and safety was, in part, a response to international concern that Pakistan’s evolving arsenal – particularly its growing inventory of short-range nuclear weapon systems – could lead to problems with warhead management and command and control during a crisis. Satellite images show that security perimeters around many bases and military facilities have been upgraded over the past seven years in response to terrorist attacks.
Over the past decade, the US assessment of nuclear weapons security in Pakistan appears to have changed considerably from confidence to concern, particularly as a result of the introduction of tactical nuclear weapons. In 2007, a US State Department official told Congress that, “we’re, I think, fairly confident that they have the proper structures and safeguards in place to maintain the integrity of their nuclear forces and not to allow any compromise” (Boucher 2007). In stark contrast, the Trump administration assessment in 2018 was: “We are particularly concerned by the development of tactical nuclear weapons that are designed for use in battlefield. We believe that these systems are more susceptible to terrorist theft and increase the likelihood of nuclear exchange in the region” (Economic Times 2017). Upon unveiling his South Asia strategy on 21 August 2017, Trump urged Pakistan to stop sheltering terrorist organizations, and noted the need to “prevent nuclear weapons and materials from coming into the hands of terrorists” (The White House 2017). US concern over the security of Pakistan’s tactical nuclear weapons precedes the Trump administration. In 2016, US Undersecretary of State Rose Gottemoeller told members of the US Congress, “Reinstate full original statement: “Battlefield nuclear weapons, by their very nature, pose [a] security threat because you're taking battlefield nuclear weapons to the field where, as you know, as a necessity, they cannot be made as secure” (Economic Times 2016).
Pakistani officials reject such concerns and insist that nuclear weapons security is adequate. Samar Mubarik Mund, the former director of the country’s National Defense Complex, explained in 2013 that a Pakistani nuclear warhead is “assembled only at the eleventh hour if [it] needs to be launched. It is stored in three to four different parts at three to four different locations. If a nuclear weapon doesn’t need to be launched, then it is never available in assembled form” (World Bulletin 2013).
As for the unique effect of tactical nuclear weapons, other Pakistani officials insist that the weapons are neither destabilizing nor lower the nuclear threshold. In 2015, General Khalid Kidwai, a member of Pakistan’s National Command Authority, explained: “Pakistan opted to develop a variety of short-range, low-yield nuclear weapons, also dubbed tactical nuclear weapons,” as a “defensive, deterrence response to an offensive doctrine” by India (Carnegie Endowment for International Peace 2015, 4).
Kidwai said the NASR short-range weapon specifically “was born out of a compulsion of this thing that I mentioned about some people on the other side toying with the idea of finding space for conventional war, despite Pakistan nuclear weapons.” Pakistan’s understanding of India’s Cold Start strategy was, he said, that Delhi envisioned launching quick strikes into Pakistan within two to four days with eight to nine brigades simultaneously (Carnegie Endowment for International Peace 2015, 8, 9). Such an attack force might involve roughly 32,000–36,000 troops.
“I strongly believe that by introducing the variety of tactical nuclear weapons in Pakistan’s inventory, and in the strategic stability debate, we have blocked the avenues for serious military operations by the other side,” Kidwai explained (Carnegie Endowment for International Peace 2015, 4–5).
After Kidwai’s statement, Pakistan’s Foreign Secretary Aizaz Chaudhry publicly acknowledged the existence of Pakistan’s “low-yield, tactical nuclear weapons,” apparently the first time a top government official has done so (India Today 2015). But the New York Times reported that although an unknown number of the tactical weapons had been built, they had not yet been deployed with warheads in the field (Sanger 2015).
In September 2016, in an interview on Geo News, Pakistani defense minister Khawaja M. Asif said, “We are always pressurised [sic] time and again that our tactical (nuclear) weapons, in which we have a superiority, that we have more tactical weapons than we need. It is internationally recognized that we have a superiority and if there is a threat to our security or if anyone steps on our soil and if someone’s designs are a threat to our security, we will not hesitate to use those weapons for our defense” (Scroll 2016).
Nuclear weapons production complex
Pakistan has a well-established and diverse fissile material production complex that is expanding. It includes the Kahuta uranium enrichment plant east of Islamabad, which appears to be growing with the addition of what could be another enrichment plant, as well as the enrichment plant at Gadwal to the north of Islamabad (Albright, Burkhard, and Pabian 2018). Four heavy-water plutonium production reactors appear to have been completed at what is normally referred to as the Khushab Complex some 33 kilometers (20 miles) south of Khushab in Punjab province. Three of the reactors at the complex have been added in the past 10 years. The addition of a publicly confirmed thermal power plant at Khushab provides new information for estimating the power of the four reactors (Albright et al. 2018a). The New Labs Reprocessing Plant at Nilore, east of Islamabad, which reprocesses spent fuel and extracts plutonium, has been expanded. Meanwhile, a second reprocessing plant located at Chashma in the northwestern part of Punjab province may have been completed (Albright and Kelleher-Vergantini 2015).
Nuclear-capable missiles and their mobile launchers are developed and produced at the National Defence Complex (sometimes called the National Development Complex) in the Kala Chitta Dahr mountain range west of Islamabad. The complex is divided into two sections. The western section south of Attock appears to be involved in development, production, and test-launching of missiles and rocket engines. The eastern section north of Fateh Jang is involved in production and assembly of road-mobile Transporter Erector Launchers (TELs), which are designed to transport and fire missiles. Satellite images show the presence of launchers for Shaheen I and Shaheen II ballistic missiles and Babur cruise missiles. The Fateh Jang section has been expanded significantly over the past 10 years, with several large launcher assembly buildings. Other launcher and missile-related production and maintenance facilities may be located near Tarnawa and Taxila.
Little is publicly known about warhead production, but experts have suspected for many years that the Pakistan Ordnance Factories near Wah, northwest of Islamabad, serve a role. One of the Wah factories is located near a unique facility with six earth-covered bunkers (igloos) inside a multi-layered safety perimeter with armed guards. The security perimeter was expanded significantly between 2005 and 2010, possibly in response to terrorist attacks against other military facilities.
Estimating the size of the Pakistani nuclear warhead stockpile is fraught with uncertainty. A frequent mistake is to derive the estimate directly from the amount of weapon-grade fissile material produced. As of the end of 2016, the International Panel on Fissile Materials estimated that Pakistan had an inventory of approximately 3,400 kilograms (kg) of weapon-grade (90 percent enriched) highly enriched uranium (HEU), and about 280 kg of weapon-grade plutonium. This material is theoretically enough to produce between 236 and 283 warheads, assuming that each first-generation implosion-type warhead’s solid core uses either 15 to 18 kg of weapon-grade HEU or 5 to 6 kg of plutonium.2
However, calculating stockpile size based solely on fissile material inventory is an incomplete methodology that tends to produce inflated numbers. Instead, warhead estimates must take several factors into account, including the amount of weapon-grade fissile material produced, warhead design choice and proficiency, warhead production rates, numbers of operational nuclear-capable launchers, how many of those launchers are dual-capable, nuclear strategy, and statements by government officials.
Estimates must assume that not all of a country’s fissile material ends up in warheads. Like other nuclear weapon states, Pakistan probably maintains a reserve. Moreover, Pakistan simply lacks enough nuclear-capable launchers to accommodate 200 to 300 warheads; furthermore, all of Pakistan’s launchers are thought to be dual-capable, which means that some of them, especially the shorter-range systems, presumably are assigned to non-nuclear missions as well. Finally, official statements often refer to “warheads” and “weapons” interchangeably, without making it clear whether it is the number of launchers or the warheads assigned to them that are being discussed.
The amount of fissile material in warheads can be reduced, and their yield increased, by using tritium to “boost” the fission process. But Pakistan’s tritium production capability is poorly understood. A German company allegedly provided Pakistan with a small amount of tritium and some tritium-processing technology in the late 1980s (Kalinowski and Colschen 1995),3 and China allegedly shipped some tritium directly to Pakistan (Kalinowski and Colschen 1995, 147, 181).
The Khushab complex for years has been rumored to produce tritium,4 and the PINSTECH complex near Nilore may do so as well (FAS 2000a). However, one rumored tritium extraction plant at Khushab turned out to be a coal-fired power plant (Burkhard, Lach, and Pabian 2017). Pakistan claimed that all its nuclear tests in 1998 were tritium-boosted HEU designs, but the yields detected by seismic signals were not sufficient to substantiate such a capability. Nonetheless, Thomas Reed and Danny Stillman conclude in The Nuclear Express that the tests included two designs, the first of which was an HEU device that used boosting. The second test involved a plutonium device (Reed and Stillman 2009, 257–258).
If Pakistan has produced tritium and uses it in second-generation single-stage boosted warhead designs, then the 3,400 kg HEU and 280 kg weapon-grade plutonium would potentially allow it to build between 339 and 353 warheads, assuming that each weapon used either 12 kg of HEU or 4 to 5 kg of plutonium.
Despite these uncertainties, Pakistan is clearly engaged in a significant build-up of its nuclear forces and has been for some time. In 2008, Peter Lavoy, then a US intelligence officer for South Asia, told NATO that Pakistan was producing nuclear weapons at a faster rate than any other country in the world (US NATO Mission 2008). Six years later, in 2014, Lavoy described the purpose of the “expansion of Pakistan’s nuclear weapons program to include efforts to significantly increase fissile material production to design and fabricate multiple nuclear warheads with varying sizes and yields, [and] to develop, test and ultimately deploy a wide variety of delivery systems with a wide range to include battlefield range ballistic delivery systems for tactical nuclear weapons”
Kidwai acknowledged in March 2015 that Pakistan “possesses a variety of nuclear weapons, in different categories. At the strategic level, at the operational level, and the tactical level” (Carnegie Endowment for International Peace 2015, 6). In December 2017 he provided more details, saying Pakistan’s nuclear strategy required the “full spectrum of nuclear weapons in all three categories – strategic, operational and tactical, with full range coverage of the large Indian land mass and its outlying territories.” He further explained that the stockpile should have “appropriate weapons yield coverage and the numbers to deter the adversary’s pronounced policy of massive retaliation.” The weapons would give the Pakistani leadership the “liberty of choosing from a full spectrum of targets, notwithstanding the [Indian] Ballistic Missile Defence, to include counter-value, counter-force, and battlefield” targets. He added this implied that “counter-massive retaliation punishment will be as severe if not more” .
How far Pakistan plans to go in terms of developing a full-spectrum deterrent posture is unclear. It has provided no public statements about its intent. In 2015, however, Kadwai said that “the program is not open ended. It started with a concept of credible minimum deterrence, and certain numbers [of weapons] were identified, and those numbers, of course, were achieved not too far away in time. Then we translated it, like I said, to the concept of full spectrum deterrence” in response to India’s Cold Start doctrine. As a result, he went on, “the numbers were modified. Now those numbers, as of today, and if I can look ahead for at least 10 to 15 more years, I think they are going to be more or less okay.” He further noted, “we’re almost 90, 95 percent there in terms of the goals that we had set out to achieve” 15 years ago (Carnegie Endowment for International Peace 2015, 6, 12).
We estimate that Pakistan currently is producing sufficient fissile material to build 14 to 27 new warheads per year,6 although we estimate that the actual warhead increase in the stockpile is probably around 10 warheads per year.
https://www.tandfonline.com/doi/full/10.1080/00963402.2018.1507796
Hans M. Kristensen,
Robert S. Norris &
Julia Diamond
Published online: 31 Aug 2018
Pakistan continues to expand its nuclear arsenal with more warheads, more delivery systems, and a growing fissile materials production industry. Analysis of a large number of commercial satellite images of Pakistani army garrisons and air force bases shows what appear to be mobile launchers and underground facilities that might be related to nuclear forces.
Table 1. Pakistani nuclear forces, 2018.
We estimate that Pakistan now has a nuclear weapons stockpile of 140 to 150 warheads.
With several delivery systems in development, four plutonium production reactors, and its uranium enrichment facilities expanding, however, Pakistan has a stockpile that will likely increase further over the next 10 years. The size of the increase will depend on many factors. Two key factors will be how many nuclear-capable launchers Pakistan plans to deploy, and how much the Indian nuclear arsenal grows. Speculation that Pakistan may become the world’s third-largest nuclear weapon state – with a stockpile of some 350 warheads a decade from now – are, we believe, exaggerated, not least because that would require a buildup two to three times faster than the growth rate over the past two decades. We estimate that the country’s stockpile could more realistically grow to 220 to 250 warheads by 2025, if the current trend continues. If that happens, it would make Pakistan the world’s fifth-largest nuclear weapon state. But unless India significantly expands its arsenal or further builds up its conventional forces, it seems reasonable to expect that Pakistan’s nuclear arsenal will not continue to grow indefinitely but might begin to level off as its current weapons programs are completed.
Nuclear policy developments
Pakistan is modifying its nuclear posture with new short-range nuclear-capable weapon systems to counter military threats below the strategic level. The efforts seek to create a full-spectrum deterrent that is designed not only to respond to nuclear attacks, but also to counter an Indian conventional incursion onto Pakistani territory.1 This development has created considerable concern in other countries, including the United States, which fears that it lowers the threshold for nuclear use in a military conflict with India.
In the Worldwide Threat Assessment for 2018, US Director of National Intelligence Daniel R. Coats said, “Pakistan continues to produce nuclear weapons and develop new types of nuclear weapons, including short-range tactical weapons, sea-based cruise missiles, air-launched cruise missiles, and longer-range ballistic missiles. These new types of nuclear weapons will introduce new risks for escalation dynamics and security in the region” (Coats 2018).
Pakistan’s National Command Authority, which includes all government agencies involved in the nuclear mission, held its 23rd meeting on 21 December 2017, under the chairmanship of then-Prime Minister Shahid Khaqan Abbasi. The group reviewed a study of “certain destabilizing actions” occurring in the region around Pakistan, including “the massive arms build-up in the conventional domain, nuclearization of the Indian Ocean Region and plans for development/deployment of [ballistic missile defense].” The National Command Authority had paid similar attention to conventional weapons development at its meeting in 2016.
At the 2017 meeting, according to a Pakistani Inter Services Public Relations press release, the command authority “reiterated Pakistan’s policy of developing and maintaining Full Spectrum Deterrence, in line with the policy of Credible Minimum Deterrence and avoidance of arms race,” while expressing confidence in the country’s “capability to address any form of aggression” (ISPR 2017d). The National Command Authority also reviewed the “Nuclear Security Regime” of the nuclear arsenal and expressed “full confidence” in both Pakistan’s command and control systems and existing security measures meant to “ensure comprehensive stewardship and security of strategic assets and materials.” It lauded the nuclear arsenal’s “high standards of training and operational readiness.”
The December 2017 meeting emphasized that Pakistan strives for “peaceful coexistence in [South Asia] and will endeavor to work with its neighbors to ensure strategic stability” there (ISPR 2017d). As in 2016, the National Command Authority’s latest statement on security and safety was, in part, a response to international concern that Pakistan’s evolving arsenal – particularly its growing inventory of short-range nuclear weapon systems – could lead to problems with warhead management and command and control during a crisis. Satellite images show that security perimeters around many bases and military facilities have been upgraded over the past seven years in response to terrorist attacks.
Over the past decade, the US assessment of nuclear weapons security in Pakistan appears to have changed considerably from confidence to concern, particularly as a result of the introduction of tactical nuclear weapons. In 2007, a US State Department official told Congress that, “we’re, I think, fairly confident that they have the proper structures and safeguards in place to maintain the integrity of their nuclear forces and not to allow any compromise” (Boucher 2007). In stark contrast, the Trump administration assessment in 2018 was: “We are particularly concerned by the development of tactical nuclear weapons that are designed for use in battlefield. We believe that these systems are more susceptible to terrorist theft and increase the likelihood of nuclear exchange in the region” (Economic Times 2017). Upon unveiling his South Asia strategy on 21 August 2017, Trump urged Pakistan to stop sheltering terrorist organizations, and noted the need to “prevent nuclear weapons and materials from coming into the hands of terrorists” (The White House 2017). US concern over the security of Pakistan’s tactical nuclear weapons precedes the Trump administration. In 2016, US Undersecretary of State Rose Gottemoeller told members of the US Congress, “Reinstate full original statement: “Battlefield nuclear weapons, by their very nature, pose [a] security threat because you're taking battlefield nuclear weapons to the field where, as you know, as a necessity, they cannot be made as secure” (Economic Times 2016).
Pakistani officials reject such concerns and insist that nuclear weapons security is adequate. Samar Mubarik Mund, the former director of the country’s National Defense Complex, explained in 2013 that a Pakistani nuclear warhead is “assembled only at the eleventh hour if [it] needs to be launched. It is stored in three to four different parts at three to four different locations. If a nuclear weapon doesn’t need to be launched, then it is never available in assembled form” (World Bulletin 2013).
As for the unique effect of tactical nuclear weapons, other Pakistani officials insist that the weapons are neither destabilizing nor lower the nuclear threshold. In 2015, General Khalid Kidwai, a member of Pakistan’s National Command Authority, explained: “Pakistan opted to develop a variety of short-range, low-yield nuclear weapons, also dubbed tactical nuclear weapons,” as a “defensive, deterrence response to an offensive doctrine” by India (Carnegie Endowment for International Peace 2015, 4).
Kidwai said the NASR short-range weapon specifically “was born out of a compulsion of this thing that I mentioned about some people on the other side toying with the idea of finding space for conventional war, despite Pakistan nuclear weapons.” Pakistan’s understanding of India’s Cold Start strategy was, he said, that Delhi envisioned launching quick strikes into Pakistan within two to four days with eight to nine brigades simultaneously (Carnegie Endowment for International Peace 2015, 8, 9). Such an attack force might involve roughly 32,000–36,000 troops.
“I strongly believe that by introducing the variety of tactical nuclear weapons in Pakistan’s inventory, and in the strategic stability debate, we have blocked the avenues for serious military operations by the other side,” Kidwai explained (Carnegie Endowment for International Peace 2015, 4–5).
After Kidwai’s statement, Pakistan’s Foreign Secretary Aizaz Chaudhry publicly acknowledged the existence of Pakistan’s “low-yield, tactical nuclear weapons,” apparently the first time a top government official has done so (India Today 2015). But the New York Times reported that although an unknown number of the tactical weapons had been built, they had not yet been deployed with warheads in the field (Sanger 2015).
In September 2016, in an interview on Geo News, Pakistani defense minister Khawaja M. Asif said, “We are always pressurised [sic] time and again that our tactical (nuclear) weapons, in which we have a superiority, that we have more tactical weapons than we need. It is internationally recognized that we have a superiority and if there is a threat to our security or if anyone steps on our soil and if someone’s designs are a threat to our security, we will not hesitate to use those weapons for our defense” (Scroll 2016).
Nuclear weapons production complex
Pakistan has a well-established and diverse fissile material production complex that is expanding. It includes the Kahuta uranium enrichment plant east of Islamabad, which appears to be growing with the addition of what could be another enrichment plant, as well as the enrichment plant at Gadwal to the north of Islamabad (Albright, Burkhard, and Pabian 2018). Four heavy-water plutonium production reactors appear to have been completed at what is normally referred to as the Khushab Complex some 33 kilometers (20 miles) south of Khushab in Punjab province. Three of the reactors at the complex have been added in the past 10 years. The addition of a publicly confirmed thermal power plant at Khushab provides new information for estimating the power of the four reactors (Albright et al. 2018a). The New Labs Reprocessing Plant at Nilore, east of Islamabad, which reprocesses spent fuel and extracts plutonium, has been expanded. Meanwhile, a second reprocessing plant located at Chashma in the northwestern part of Punjab province may have been completed (Albright and Kelleher-Vergantini 2015).
Nuclear-capable missiles and their mobile launchers are developed and produced at the National Defence Complex (sometimes called the National Development Complex) in the Kala Chitta Dahr mountain range west of Islamabad. The complex is divided into two sections. The western section south of Attock appears to be involved in development, production, and test-launching of missiles and rocket engines. The eastern section north of Fateh Jang is involved in production and assembly of road-mobile Transporter Erector Launchers (TELs), which are designed to transport and fire missiles. Satellite images show the presence of launchers for Shaheen I and Shaheen II ballistic missiles and Babur cruise missiles. The Fateh Jang section has been expanded significantly over the past 10 years, with several large launcher assembly buildings. Other launcher and missile-related production and maintenance facilities may be located near Tarnawa and Taxila.
Little is publicly known about warhead production, but experts have suspected for many years that the Pakistan Ordnance Factories near Wah, northwest of Islamabad, serve a role. One of the Wah factories is located near a unique facility with six earth-covered bunkers (igloos) inside a multi-layered safety perimeter with armed guards. The security perimeter was expanded significantly between 2005 and 2010, possibly in response to terrorist attacks against other military facilities.
Estimating the size of the Pakistani nuclear warhead stockpile is fraught with uncertainty. A frequent mistake is to derive the estimate directly from the amount of weapon-grade fissile material produced. As of the end of 2016, the International Panel on Fissile Materials estimated that Pakistan had an inventory of approximately 3,400 kilograms (kg) of weapon-grade (90 percent enriched) highly enriched uranium (HEU), and about 280 kg of weapon-grade plutonium. This material is theoretically enough to produce between 236 and 283 warheads, assuming that each first-generation implosion-type warhead’s solid core uses either 15 to 18 kg of weapon-grade HEU or 5 to 6 kg of plutonium.2
However, calculating stockpile size based solely on fissile material inventory is an incomplete methodology that tends to produce inflated numbers. Instead, warhead estimates must take several factors into account, including the amount of weapon-grade fissile material produced, warhead design choice and proficiency, warhead production rates, numbers of operational nuclear-capable launchers, how many of those launchers are dual-capable, nuclear strategy, and statements by government officials.
Estimates must assume that not all of a country’s fissile material ends up in warheads. Like other nuclear weapon states, Pakistan probably maintains a reserve. Moreover, Pakistan simply lacks enough nuclear-capable launchers to accommodate 200 to 300 warheads; furthermore, all of Pakistan’s launchers are thought to be dual-capable, which means that some of them, especially the shorter-range systems, presumably are assigned to non-nuclear missions as well. Finally, official statements often refer to “warheads” and “weapons” interchangeably, without making it clear whether it is the number of launchers or the warheads assigned to them that are being discussed.
The amount of fissile material in warheads can be reduced, and their yield increased, by using tritium to “boost” the fission process. But Pakistan’s tritium production capability is poorly understood. A German company allegedly provided Pakistan with a small amount of tritium and some tritium-processing technology in the late 1980s (Kalinowski and Colschen 1995),3 and China allegedly shipped some tritium directly to Pakistan (Kalinowski and Colschen 1995, 147, 181).
The Khushab complex for years has been rumored to produce tritium,4 and the PINSTECH complex near Nilore may do so as well (FAS 2000a). However, one rumored tritium extraction plant at Khushab turned out to be a coal-fired power plant (Burkhard, Lach, and Pabian 2017). Pakistan claimed that all its nuclear tests in 1998 were tritium-boosted HEU designs, but the yields detected by seismic signals were not sufficient to substantiate such a capability. Nonetheless, Thomas Reed and Danny Stillman conclude in The Nuclear Express that the tests included two designs, the first of which was an HEU device that used boosting. The second test involved a plutonium device (Reed and Stillman 2009, 257–258).
If Pakistan has produced tritium and uses it in second-generation single-stage boosted warhead designs, then the 3,400 kg HEU and 280 kg weapon-grade plutonium would potentially allow it to build between 339 and 353 warheads, assuming that each weapon used either 12 kg of HEU or 4 to 5 kg of plutonium.
Despite these uncertainties, Pakistan is clearly engaged in a significant build-up of its nuclear forces and has been for some time. In 2008, Peter Lavoy, then a US intelligence officer for South Asia, told NATO that Pakistan was producing nuclear weapons at a faster rate than any other country in the world (US NATO Mission 2008). Six years later, in 2014, Lavoy described the purpose of the “expansion of Pakistan’s nuclear weapons program to include efforts to significantly increase fissile material production to design and fabricate multiple nuclear warheads with varying sizes and yields, [and] to develop, test and ultimately deploy a wide variety of delivery systems with a wide range to include battlefield range ballistic delivery systems for tactical nuclear weapons”
Kidwai acknowledged in March 2015 that Pakistan “possesses a variety of nuclear weapons, in different categories. At the strategic level, at the operational level, and the tactical level” (Carnegie Endowment for International Peace 2015, 6). In December 2017 he provided more details, saying Pakistan’s nuclear strategy required the “full spectrum of nuclear weapons in all three categories – strategic, operational and tactical, with full range coverage of the large Indian land mass and its outlying territories.” He further explained that the stockpile should have “appropriate weapons yield coverage and the numbers to deter the adversary’s pronounced policy of massive retaliation.” The weapons would give the Pakistani leadership the “liberty of choosing from a full spectrum of targets, notwithstanding the [Indian] Ballistic Missile Defence, to include counter-value, counter-force, and battlefield” targets. He added this implied that “counter-massive retaliation punishment will be as severe if not more” .
How far Pakistan plans to go in terms of developing a full-spectrum deterrent posture is unclear. It has provided no public statements about its intent. In 2015, however, Kadwai said that “the program is not open ended. It started with a concept of credible minimum deterrence, and certain numbers [of weapons] were identified, and those numbers, of course, were achieved not too far away in time. Then we translated it, like I said, to the concept of full spectrum deterrence” in response to India’s Cold Start doctrine. As a result, he went on, “the numbers were modified. Now those numbers, as of today, and if I can look ahead for at least 10 to 15 more years, I think they are going to be more or less okay.” He further noted, “we’re almost 90, 95 percent there in terms of the goals that we had set out to achieve” 15 years ago (Carnegie Endowment for International Peace 2015, 6, 12).
We estimate that Pakistan currently is producing sufficient fissile material to build 14 to 27 new warheads per year,6 although we estimate that the actual warhead increase in the stockpile is probably around 10 warheads per year.
https://www.tandfonline.com/doi/full/10.1080/00963402.2018.1507796
