The Risk of Nuclear War Between India and Pakistan

May 9, 2025

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Nuño Sempere, Vidur Kapur, and Lisa discuss the possibility of nuclear escalation between India and Pakistan.

Timestamps

(00:16:00) - Intro

(00:43:00) - Background on the conflict

(02:26:13) - Direct forecasts of nuclear weapons use

(15:45:10) - The role of other nations

(20:26:09) - What if Pakistan collapses?

(22:45:16) - Russia's incentives in global conflicts

(25:40:08) - What are the forecasters looking out for next?

(29:28:06) - Outro

Transcript

The transcript is AI-generated and slightly differs from the phrasing used in the recording.

Rai Sur

00:00:16

Welcome to the Sentinel podcast, where top forecasters discuss ongoing events with a view towards better understanding global catastrophic risk. Today, we'll be talking about the recent military escalation between two nuclear weapons states, India and Pakistan. I'm your host, Rai, and I'm joined by three of Sentinel's world-class forecasters: Nuño Sempere, who's also my co-founder at Sentinel; Lisa, also known by her forecasting moniker, Be Like Water; and Vidur Kapur. The situation is evolving rapidly, and we are recording this on Wednesday, May 7th.

To ground the discussion, the focus will be on nuclear risk, as Sentinel is concerned with escalations in the long tail of extremely bad outcomes. Most of that risk here is nuclear.

About two weeks ago, a terrorist attack in Jammu and Kashmir, a contested territory on the India-Pakistan border, killed 27 people (mostly Hindus) and injured 20 others. This caused an immediate diplomatic breakdown that has since escalated to military action at a scale not seen since the last Indo-Pakistani war in 1999.

India's nuclear program conducted its first nuclear test in 1974, and Pakistan had theirs in 1998, but neither has tested a weapon since 1998. The countries have very different nuclear doctrines. India committed to a no-first-use doctrine in 1998, meaning they pledged not to use nuclear weapons proactively. Pakistan, however, affirmed as recently as this conflict that it expressly does not have a no-first-use doctrine. With a significantly weaker conventional military, Pakistan uses the threat of nuclear first use as a deterrent.

Regarding their nuclear arsenals: India and Pakistan both possess numerous warheads and missiles capable of covering each other's entire territories. As of 2013, Pakistan stated it would need to assemble a nuclear-armed missile from parts stored in different locations, though it's unclear if this remains true. India has new missiles that can be permanently mated with warheads and stored ready for use. It's unclear if any of these missiles are currently mated to nuclear warheads.

With that background established, I'm curious where you all are starting on this question. What's your rough estimate of the probability of at least one nuclear weapon being launched by either India or Pakistan in the next 365 days? How are you arriving at that, and what are you considering? Let's start with Nuno.

Nuño Sempere

00:02:44

Before this recent escalation, I was at approximately 0.1%. I arrived at that by decomposing the question into: first, the chances of a significant escalation, and second, conditional on that escalation, the chances of a nuke being used.

In our forecast a week ago, we defined the threshold for significant escalation as 1,000 deaths. This is much higher than the 27 deaths seen so far. However, India's response seems more kinetic than I expected.

If I was previously at a 12% chance of significant escalation and a 1% chance of nuclear use conditional on that, my estimate for hitting that 1,000-death threshold might now be around 15% to 20%. This brings my overall estimate from 0.1% to perhaps 0.2%.

Overall, I believe it's still unlikely because both sides really don't want it. However, there's a dynamic where both sides are uncertain, capable of making mistakes, and could start on a path they cannot stop.

Rai Sur

00:03:58

Vidur, what about you?

Vidur Kapur

00:03:59

There are a few different ways to approach this question. One is, like Nuno, to take this in stages. You could look at the probability of a significant escalation—for example, 1,000 military fatalities within the next 12 months—and then, conditional on that, the probability of nuclear weapon use.

For me, I'm now at around 20% for 1,000 military fatalities within the next 12 months. Conditional on that, I'm at possibly around 2% to 3% for actual nuclear weapon use.

This puts me a fair bit higher than Nuno, at around 0.4% to 0.6% overall. Taking the average, I estimate a 0.5% chance of nuclear weapon use by either India or Pakistan within the next 12 months.

Rai Sur

00:05:11

It might be good to contextualize this second part: where the nuclear use percentages come from.

Vidur Kapur

00:05:16

Absolutely.

Rai Sur

00:05:17

There seems to be a range of numbers most forecasters coalesce around for nuclear weapon use. How do you arrive at those figures? What's their origin?

Vidur Kapur

00:05:29

The second part is to determine the base rate for nuclear weapons use in a conflict. In the past 80 years, coinciding with the 80th anniversary of the end of World War II, there has been essentially one instance of nuclear weapon use in conflict—the two bombs in Japan, which I count as one event. This gives a base rate of 1 in 80, or about 1.25%.

Looking closer, when the United States used nuclear weapons, it was the sole nuclear state. Japan couldn't retaliate as it lacked nuclear weapons, possessing only a crude program. The Soviet Union, Germany, and Britain also didn't have them at that time. This suggests the probability of nuclear use in the modern age is lower than 1.25% because states are hesitant to break the norm against their use.

In the India-Pakistan case, both have nuclear weapons, meaning mutual use would cause immense destruction on both sides. This might push the probability lower. However, Pakistan's military doctrines suggest a willingness to use nuclear weapons under certain circumstances. One scenario involves a battlefield commander using tactical nuclear weapons, which Pakistan possesses. Doctrines indicate a willingness to use them, especially against an existential threat to Pakistan.

One could also imagine a general, in the fog of war, deploying tactical nuclear weapons to halt an Indian advance. If India made an incursion, a general, perhaps misinformed about broader Indian gains, might panic and use them. This specific scenario is concerning and pushes my estimate higher than 1.25%.

Generally, the ongoing conflict itself suggests a higher probability. If India and Pakistan were at peace, nuclear use would be unlikely, barring an accident. But with an active conflict and reports of downed Indian jets, we should consider a rate higher than 1.25%, possibly 2% to 3%.

We also know that former Secretary of State Mike Pompeo stated in his memoir that during the 2019 India-Pakistan escalation, both countries were very close to using nuclear weapons. While he might have exaggerated for his memoir, it's another data point suggesting these countries are among those most liable to use nuclear weapons in a conflict scenario.

Nuño Sempere

00:09:25

Fedor, that 1.25% is for all countries collectively. What share of that risk do you assign specifically to India and Pakistan? Considering the large number of nuclear states, the base rate per year for a state *not* using nuclear weapons is quite high.

Conversely, there have been events close to nuclear weapon use. North Korea's nuclear tests to deter the US are an example. More recently, Russia's seizure of the Zaporizhzhia nuclear plant could also be considered, potentially expanding the reference class. What are your thoughts on this, especially regarding the share of the 1.25% attributable to India and Pakistan?

Vidur Kapur

00:10:22

My estimate of 0.4% to 0.6% implies a significant share for India and Pakistan. Much of the remaining risk, in my view, currently lies with Russia in Ukraine, as Russia has explicitly discussed using nuclear weapons. In autumn 2022, Western policymakers were very concerned about Russian nuclear use; the British Prime Minister was reportedly monitoring weather patterns due to fears of nuclear fallout. So, Russia and Ukraine account for a large share.

However, aside from these two, it's justifiable for India and Pakistan to represent a substantial portion of the nuclear risk within the next year, given their current conflict. As we speak, Indian pilots may be hospitalized due to downed fighter jets. Indian officials have briefed The New York Times and The Hindu that at least three fighter jets are down.

While they don't constitute the entire risk, they justifiably form a major part of the nuclear risk for the coming year.

Rai Sur

00:11:44

Lisa, what are your thoughts here?

Lisa

00:11:46

My forecast for nuclear weapon usage risk aligns closely with Nuno's, around 0.1% to 0.2%. I'll say 0.2% due to recent escalation. However, my overall view is that because both are nuclear powers, the risk of them ever using nuclear weapons is extremely low; the consequences are too high. An incredible escalation would be necessary before we'd see nuclear weapons used.

Consider Ukraine versus Russia: despite numerous threats of Russian nuclear use contingent on Ukrainian actions, it hasn't happened. No rational country wants to use nuclear weapons in almost any scenario. Therefore, the risk is extremely small.

Most of the current risk, in my opinion, stems from accidents or misunderstandings. For instance, if one country inaccurately perceived the other's actions, it might lead to a misjudgment and nuclear use. This is the most likely path to nuclear weapon use in this conflict.

Another factor is the significant imbalance in country size, military size, and military budgets. Pakistan spends $10 billion annually on defense, while India spends $81 billion. Due to this asymmetry and other reasons, neither side wants this conflict to escalate. They will likely try to de-escalate after responses that satisfy domestic political needs.

This is my framework: events have occurred, and each side must respond to some degree, but neither wants an uncontrolled escalation. I don't see a substantial risk of this escalating to actual nuclear war.

Vidur Kapur

00:14:18

A counterargument is that in the Russia-Ukraine scenario, while both sides really, really hate each other, Ukraine was held back. The United States supplied many of Ukraine's weapons and calibrated its support to avoid nuclear escalation. President Biden recently acknowledged in a BBC interview his deep concern about World War III and nuclear escalation, stating he didn't want to "play roulette."

With India and Pakistan, you have two sides that really hate each other, and emotions run high. Neither side wants nuclear escalation. However, if mistakes occur, or events deviate from plans, such as fighter jets being shot down, it creates an incentive to respond more forcefully.

While the chance of this leading to nuclear escalation is very small, if fighter jets are shot down, India might feel compelled to respond even more strongly. Pakistan already feels the need to respond to airstrikes on its territory. This could escalate because both sides feel the need to save face, perceiving themselves as losers in the scenario, and there's no one effectively holding them back.

The United States might intervene, but it is currently preoccupied with other crises like Gaza, Iran, and Ukraine. This creates a potential path toward nuclear escalation, driven by the need to save face and heightened emotions.

Lisa