This is what Pakistan and India's atomic arsenals look like: a nuclear war between them would kill 20 million in a week.

India and Pakistan remain mired in an escalating tension that intensified after the former launched a series of airstrikes against terrorist infrastructure in the northern neighbor's territory early Wednesday morning. Islamabad claims that the Indian airstrikes targeted civilian populations, killing 31 people and injuring 57 more.

Since then, the airspace activity has continued. The recent escalation was triggered by a massacre in Indian-administered Kashmir on April 22 , in which 26 people, mainly Indian tourists, died. India blames Pakistan for being behind this attack.

The conflict has been going on for 78 years. The Partition of India, a colony of the British Empire, took place in 1947. Since that separation into two states, the wound of Kashmir has not stopped bleeding. For New Delhi, this region (with a Muslim majority) is an "integral part" of India, while Pakistan's official position is that Kashmir is a disputed territory whose final status can only be determined by the Kashmiri people.

Nuclear powers outside the Treaty

The two countries have already fought four wars (1947, 1965, 1971, and 1999). But now we are facing a major conflict due to the fact that these two nuclear powers are facing each other, and they are not party to the Nuclear Non-Proliferation Treaty (NPT). Therefore, neither India nor Pakistan are subject to international restrictions on the development and expansion of nuclear weapons.

Although both nations' arsenals are designed to act as a deterrent, the spark can explode at any moment. The Stockholm International Peace Research Institute (SIPRI) estimates that even a small nuclear exchange between the two countries could result in the deaths of 20 million people within a week.

Pakistani Defense Minister Khawaja Muhammad Asif has said his country is "trying to avoid" an all-out war with India, but that its military is "prepared" for such a scenario. "We are prepared for an all-out war. There's no doubt about it, because India is escalating the stakes of this conflict. So we can't be caught off guard," he told CNN .

Pakistan does not maintain a "no first use" policy for nuclear weapons, as India does. However, in 2019, Indian Defense Minister Rajnath Singh questioned this doctrine, stating that "what happens in the future will depend on the circumstances."

India's nuclear arsenal

India has been a nuclear power since 1974. The country continues to rely on this type of weapon, largely as a show of force against China , a country with which it also clashes in Kashmir (in Aksai Chin).

SIPRI estimates that India has 164 nuclear warheads in its arsenal. This figure was based on estimates of India's stockpile of weapons-grade plutonium and the number of operational nuclear delivery systems, but it may already be exceeded. In fact, the Federation of American Scientists (FAS) puts the number of warheads at around 180.

" India continues to modernize its nuclear arsenal, with at least four new weapons systems and several new delivery platforms under development to complement or replace existing nuclear-capable aircraft, land-based delivery systems, and sea-based systems," the FAS said in its Nuclear Notebook .

New Delhi has the capacity to do more. The Bulletin of the Atomic Scientist estimates that India could have produced enough military plutonium to make between 130 and 210 nuclear warheads, but it has likely only produced about 172.

India has the so-called nuclear triad: nuclear-powered missiles and rockets that can be launched from land, sea, and air. India's nuclear weapons are believed to be plutonium-based. Production is believed to be concentrated at the Bhabha Atomic Research Centre.

Pakistan's nuclear arsenal

The country has increased its stockpile of fissile material and developed new delivery systems, revealing its desire to expand its nuclear arsenal. Islamabad has been investing in short-range tactical nuclear weapons to counter Indian conventional forces in the event of a conflict.

It possesses some 170 nuclear warheads, according to figures shared by SIPRI, the FAS, and the BAS . Pakistan began developing its nuclear arsenal in 1998 and has increased its nuclear capabilities in recent years.

With several new delivery systems under development, four plutonium production reactors, and an expanding uranium enrichment infrastructure, " Pakistan's arsenal may grow further in the coming years," the BAS report notes . According to its estimates, at the current rate, it could reach 200 nuclear warheads by the end of the 2020s.

Current nuclear warhead designs are believed to use highly enriched uranium . Pakistan continues to produce highly enriched uranium for military purposes, and its total stockpile was estimated at 2.7–3.5 tonnes in 2014, SIPRI reports. Enrichment takes place at gas centrifuge facilities in Kahuta and Gadwal, Punjab.

There is a widespread belief that, in peacetime, Pakistan stores its nuclear warheads separate from their delivery vehicles . However, SIPRI explains, the Strategic Plans Division, which operates Pakistan's nuclear forces, has never confirmed such arrangements.