Over 100 Million Dead: What Would Happen if India and Pakistan Waged a Nuclear War?

Amid rising tensions between South Asia’s two nuclear-armed neighbours, India launched an alarming escalation on Thursday morning, ordering all Pakistani nationals residing in India to leave by April 29. The move came in response to a deadly attack in Pahalgam, an area in the disputed Kashmir region under Indian administration, where 26 people were killed, reigniting fears in a land already marked by decades of unrest.

India also suspended a key water-sharing treaty, closed its main land border crossing with Pakistan, drastically reduced diplomatic staff, and ordered Pakistani diplomats and military attachés to return home.

Islamabad quickly issued a stern response, warning that any threat to its sovereignty would trigger a “deterrent response,” and declaring that any Indian attempt to divert the flow of the Indus River would be deemed an act of war. Pakistan further closed its airspace and borders to India, suspended bilateral trade, and expelled several Indian diplomats.

Meanwhile, Indian Prime Minister Narendra Modi appeared in a defiant tone, promising to hunt down those responsible for the attack, warning that the punishment would be “beyond their imagination.” Indian officials, speaking anonymously to Al Jazeera, claimed that four attackers were involved — two from Pakistan, and two from Indian-administered Kashmir.

Officially, Pakistan denied any involvement in the attack, expressed condolences for the victims, and convened an emergency meeting of its National Security Council to formulate a calculated response. A group calling itself the “Resistance Front” (TRF), believed to be linked to Lashkar-e-Taiba, claimed responsibility, citing opposition to the recent granting of thousands of residency permits to Indians in Kashmir.

This latest episode is but one chapter in a long history of escalations, particularly over Kashmir. It recalls the deadly events of February 2019, when over 40 Indian soldiers were killed in a bombing, leading India to launch airstrikes inside Pakistani territory.

Perhaps the most chilling revelation came later: Former U.S. Secretary of State Mike Pompeo wrote in his memoirs that the two nations were “one step away” from a nuclear confrontation at that time, with India allegedly preparing a retaliatory nuclear strike after Pakistani forces reportedly readied their arsenal.

India’s “Credible Minimum Deterrence” Doctrine

India’s pursuit of nuclear capability dates back to 1944. Though its first nuclear test, “Smiling Buddha,” did not occur until 1974, it marked a turning point that triggered international outrage and U.S. sanctions.

However, it was in 1998 that India’s nuclear posture truly crystallised, following a series of tests and the articulation of its doctrine of Credible Minimum Deterrence — a commitment to maintaining a small but effective nuclear arsenal solely for retaliation in the event of a nuclear attack. India explicitly pledged no first use of nuclear weapons, aiming to deter war rather than wage it, by making any nuclear aggression prohibitively costly.

This Indian doctrine, focused on capability rather than quantity, avoids an open nuclear arms race but maintains enough firepower to assure massive retaliation if attacked — especially vital in a region as volatile as South Asia.

Pakistan’s “First Use” Doctrine: A Different Approach

In contrast, Pakistan’s nuclear programme emerged from existential insecurity after its defeat and territorial loss in the 1971 war, which gave birth to Bangladesh.

Triggered by India’s nuclear advancements, Pakistan pursued a rapid, clandestine path to nuclear capability. By the 1980s, it was believed to possess nuclear weapons technology, although it remained undeclared until India’s 1998 tests, which Pakistan answered with its own series of detonations.

Unlike India, Pakistan adopted a First Use Doctrine — reserving the right to initiate a nuclear strike if its territorial integrity, economy, military forces, or political stability faced an existential threat. This posture, built on “deterrence through ambiguity,” aimed to dissuade Indian aggression by keeping the threat of nuclear escalation ever-present.

Nuclear Arsenals: Deadly Triads

Currently, India and Pakistan together possess between 300 to 400 nuclear warheads, fairly evenly distributed.

Both countries have developed aspects of the “nuclear triad” — the ability to launch nuclear strikes by land-based missiles, air-delivered bombs, and submarine-launched missiles.

India boasts the formidable Agni missile series, culminating in the Agni-5 with an 8,000 km range, and deploys nuclear-capable submarines like INS Arihant. Aircraft such as the Mirage 2000H and Su-30 are also modified to carry nuclear payloads.

Pakistan fields the Shaheen and Ghauri missile series, along with the Babur-3 cruise missile launched from submarines. Its F-16s and Mirage III/V aircraft are likewise nuclear-capable.

Pakistan’s development of low-flying, radar-evading cruise missiles adds a dangerous layer of complexity, enhancing its ability to strike with precision.

If a Nuclear War Broke Out

In 2019, a chilling simulation by the Bulletin of the Atomic Scientists envisaged a full-scale India-Pakistan nuclear war by 2025.

• • It imagined a terrorist attack on India’s parliament triggering an Indian armored invasion into Pakistani-held Kashmir.

• • In response, Pakistan, facing conventional military defeat, would deploy tactical nuclear weapons.

• • India would retaliate massively, striking Pakistani military and urban centres.

Within the first week, the death toll would range between 50 to 125 million people, the study warned.

Fires from devastated cities would inject 16–36 million tons of black carbon into the upper atmosphere, dimming sunlight, plunging global temperatures, and disrupting agriculture worldwide — triggering famine and societal collapse even in countries far removed from the conflict.

The Razor’s Edge of Reality

While such a catastrophe remains theoretical, history reminds us how perilously close India and Pakistan have come to the brink. They have fought four wars (1947, 1965, 1971, and 1999) and engaged in countless skirmishes.

As tensions once again spiral, and with nationalist fervour rising, the risk that miscalculation or rage could ignite a nuclear inferno is ever-present.

In a world saturated with injustice and instability, the spectre of a South Asian nuclear war serves as a grim reminder: without justice, diplomacy, and restraint, humanity stands forever on the edge of its own annihilation.

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