In an increasingly volatile geo-political environment, the emergence of India as the eighth nuclear-armed state to develop multiple independently targetable re-entry vehicle (MIRV) technology marks a significant shift in the global strategic balance. On March 11, India successfully tested the Agni-5 MIRV missile. Named mission Divyastra, the technology was under development for over a decade by the Defence Research and Development Organisation. MIRV allows a single missile to carry multiple warheads and target them independently and the proliferation of this tech underscores a broader trend in the evolution of nuclear and missile capabilities across the globe. In an interaction with Fortune India, Hans M. Kristensen, associate senior fellow in the SIPRI Weapons of Mass Destruction Programme and also director at the Federation of American Scientists in Washington, D.C, shares his views on why India's entry into the MIRV club signifies not only a technical milestone but also a potential alteration in the regional power dynamics, particularly with respect to China and Pakistan.

How does India's deployment of MIRV technology reflect broader trends in global nuclear armament and missile technology development?

India's development of MIRV is the 8th nuclear-armed state that is doing so. The United States and the Soviet Union spearheaded this technology back in the 1970s and were soon followed by France and the United Kingdom. Then came China's deployment of MIRV on its DF-5B in 2015, Pakistan's Ababeel flight-test in 2017, and now India's Agni-5 test after the developmental Agni-P test in 2021. And, apparently, North Korea is also working on multiple warhead technology. Although there are still technical challenges before MIRV becomes fully operational in India, Pakistan, and North Korea, the trend is that the MIRV club has doubled in the past decade as more and more nuclear-armed states are pursuing multiple-warhead capability for their nuclear weapons.

What are the specific technical capabilities of India's Agni-5 missile with MIRV technology, and how does this advancement alter the strategic balance in the region?

Although there are many rumours, very little is known in public about the specifics of the Indian MIRV technology. How many warheads can Agni-5 carry, how accurate are the MIRVs, what kinds of targets can they hold at risk, and how does MIRV affect the range of the Agni-5? The US Intelligence Community has designated Agni-5 as an intermediate-range missile but with near-intercontinental ballistic missile (ICBM) range (5,000+ km), which gives the missile the capability (once it becomes operational) to deliver warheads to all of China (and Pakistan). MIRV only makes operational sense if intended to hold more targets at risk and/or try to overcome missile defence systems. As such, India's development of MIRV appears to be driven mainly by its nuclear relationship with China, which is increasing its nuclear posture and developing missile defences. MIRV, potentially, also gives India an improved capability to increase its nuclear arsenal faster than by fielding more single-warhead missile launchers to more bases. Although it is still early, India's MIRV potentially could become an important capability in an increased nuclear competition with China. It seems almost inevitable that this could cause both countries to increase the nuclear forces they aim at each other.

What is the consequence of MIRVs in the context of nuclear deterrence theory and crisis stability? Also, could the deployment of MIRV be seen as a rational response to evolving security challenges, rather than an escalation of an arms race?

The issues are not, in my view, whether MIRVing is a rational response to security changes but whether it will create a future security environment and dynamic that will increase or reduce nuclear risks. No nuclear-armed country wants a nuclear arms race and will always insist that its nuclear arsenal and modernisation are at the minimum level required for deterrence and not in any way de-stabilising. But nuclear modernisation will inevitably stimulate a reaction in other nuclear-armed states. And countries may not necessarily be able to foresee or control this dynamic but be forced to respond in ways they did not intend. Because MIRV potentially can be used to rapidly increase a nuclear arsenal and significantly increase the number of targets that can be held at risk and destroyed quickly, the capability can create powerful action-reaction cycles that can result in instability in force levels, strike planning and strategy, as well as how countries might react in a crisis and war. More warheads on each missile will also make each missile more important to attack for an adversary that wants to destroy India's ability to retaliate. Greater numbers of warheads on missiles on high alert will almost inevitably make crisis stability more brittle and risk of incidents, misunderstandings, and overreaction much more consequential. We know from the Cold War how MIRV affected U.S.-Soviet relations and planning, triggered a massive nuclear buildup with forces on high alert and increased fear about first strike. This fear, in turn, triggered a series of arms control initiatives where the two sides tried to control the dynamic by limiting their strategic nuclear arsenals. That might potentially be the future reaction to an increased nuclear stand-off between China and India.

How do you assess the impact of India's MIRV capabilities on its nuclear doctrine, particularly regarding no-first-use and retaliatory strike policies?

It obviously seems strange that a country with a minimum deterrence policy would want to or have to develop MIRV capability. The effect of the technology is that India will be able to deploy more nuclear warheads on its missiles. If this were driven by strategy, one could imagine Indian planners wanted to increase the number of targets they could hold at risk in China. Or that it was necessary to overcome the effect of future Chinese missile defences. Or a combination of the two. In the future, India could potentially deploy MIRV on the Agni-5 and the future Agni-6 (if they field it). In the case of China, the U.S. military says that more warheads on solid-fuel missiles supported by a space-based early-warning system imply a launch-on-warning strategy and raises questions about the no-first-use policy. While that is hypothetically possible, it is unknown if that will change the policy. MIRV doesn't in itself indicate that India is abandoning the no-first-use policy or significantly changing its response options, but MIRV would greatly exacerbate the effect if the policy did change - especially if MIRV is deployed on quick-launch solid-fuel missiles.

Could you discuss the historical context and implications of the failure of the US and Russia to implement a ban on MIRV land-based missiles, as agreed in the START-II treaty?

The two sides agreed to ban MIRV on land-based missiles to increase crisis stability and reduce their arsenals under START-II. Russia stalled ratification of START-II for years and the two, eventually, abandoned the treaty and replaced it with the simple SORT (Moscow) treaty that only had overall limits, but no MIRV ban. The New START treaty continued this approach and left it to each side to structure the forces any way they wanted as long as they stayed under the total ceiling. The U.S. inherited a significant advantage in strategic launchers and could upload many more reserve warheads than Russia. The Russian reaction was, in turn, to replace single-warhead missiles with multiple-warhead missiles (on a less than one-for-one basis) and increase the capacity to upload reserve warheads to better balance the US posture. Now that the New START treaty limits seem to fall away in two years, both sides are predictably increasingly turning to more worst-case scenarios in their long-term planning - scenarios that include potentially increasing the number of MIRVs deployed on the missiles. China's increase is adding significant pressure to that dynamic.

In what ways do you see the proliferation of MIRV technology influencing future arms control negotiations and nuclear non-proliferation efforts?

Proliferation of MIRV can potentially influence the future of arms control in several ways. If proliferation of MIRV triggers increases of nuclear arsenals, it could potentially trigger regional efforts to reach agreements to place limits on warhead levels. We saw that reaction in the US-Soviet era. De-MIRVin would be a logical option that could, in fact, be verified by using a similar inspection system to what was developed for the New START treaty. If MIRV proliferation triggers more dangerous targeting and launch strategies, that could be much more difficult to limit or control. Either way, arms control reactions are probably unlikely unless MIRV leads to a significant nuclear build-up or particularly dangerous strategies. Some people will probably argue that MIRV has been deployed for years in the post-Cold War era without causing significant problems, but that ignores that this happened during a period of decreased tension and significantly declining nuclear arsenals; during the past decade, this situation has fundamentally changed, and the world is once again heading toward bigger nuclear arsenals and increased tension.

How do you evaluate the risks of a potential arms race involving MIRV technology among nuclear-armed states, particularly India, China, Pakistan, and North Korea?

India and Pakistan are already in a two-decade-old regional nuclear arms competition in which both countries have been increasing their arsenals and are developing and probably soon deploying MIRV. China's MIRV capability so far is, probably, primarily focused on its competition with the U.S., but it is increasing to other missiles and as its arsenal grows it seems inevitable that it will also influence Indian thinking about the size and capability of its nuclear arsenal. North Korea's possible development of MIRV (or MRV) capability is, probably, primarily driven by its adversarial relationship with the US. But combined, these regional developments will add up to more nuclear weapons on more capable missiles, which, in turn, is likely to deepen suspicion about intentions, worst-case planning, and trigger countermeasures. In addition, both China and India are developing breeder-reactors that will significantly increase their inventory of weapons-grade plutonium that, potentially, will allow both to significantly increase their nuclear arsenals in the future. China has already decided to do so; how will India react?

What are the implications of MIRV technology for anti-ballistic missile defence systems and the overall architecture of global missile defence?

Missile defence is one of the factors that appear to motivate countries to develop MIRV and increase their nuclear forces. Overwhelming missile defences was one of the reactions of the U.S. back in the 1970s after the Soviet Union developed limited missile defence systems around Moscow and (then) Leningrad. Initially, the U.S. responded by creating a strike plan that included over 100 ICBMs and submarine-launched missiles to defeat those defences. As MIRV increased, the additional warheads allowed the planned to saturate target categories with warheads. Britain initially focused its nuclear strategy on overwhelming the missile defence system around Moscow. The Chinese development of road-mobile ICBMs was triggered by the U.S. deployment of MIRVed Trident missiles into the Pacific in the 1980s, and after the U.S. abandoned the ABM treaty and began developing national and regional missile defence systems, China reacted by deploying more ICBMs and equipping some of them with MIRV. So, ironically, while missile defences are said to be needed to protect, they trigger development of countermeasures that significantly increase the destructive effects of nuclear arsenals. Missile defence may have some effect against small attacks, but it is a dangerous illusion to believe they protect against nuclear weapons.

Can bilateral or multilateral disarmament agreements address the challenges posed by MIRVs without compromising national security?

Bilateral or multilateral agreements could potentially address the challenges posted by MIRV by verifiably limiting or eliminating MIRV without depriving the nuclear-armed states of the ability to maintain a security retaliatory capability. Countries could potentially reach bilateral agreements, but a multilateral agreement would obviously be better because it would prevent MIRVing in one region from undermining de-MIRVing in another region. Limiting missile defences is another necessity because too effective missile defences can threaten the effectiveness of limited retaliatory nuclear forces and therefore motivate countries to increase their arsenals and add MIRV. But the arms control challenge is bigger than just nuclear: it is an illusion to imagine that countries would limit their nuclear arsenals if long-range conventional strike forces continue to develop and increasingly threaten nuclear retaliatory forces. To break this cycle, agreements would have to address the relationship between nuclear, conventional, and missile defences. But that risks making arms control so complicated that nothing is possible. At the end of the day, it comes down to political will: if leaders believe it is important to achieve results and order their government to make it happen, then it can happen. If they’re not, then we're inevitably heading into another Cold War.

How will the international community respond to the challenges posed by MIRV technology to maintain strategic stability and prevent nuclear escalation?

The international community will obviously react in some fashion if it sees nuclear arms races and increased dangers resulting from MIRV. For example, it might trigger growing criticism of nuclear-armed states and demands that they do something to limit the risks, for example by signing new agreements that cap their arsenals or reduce dangerous behaviours. Though, in reality, the international community has few options to force the nuclear-armed states to change if they don't agree to do so. The new international Treaty on the Prohibition of Nuclear Weapons is a good example: the nuclear-armed states oppose it because it would require them to change and they don't want to do that under the current conditions.

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