India and Pakistan continued to develop new types of nuclear weapon delivery systems in 2025 and are pursuing the capability to deploy multiple warheads on ballistic missiles, according to a report released on Monday by the Stockholm International Peace Research Institute (SIPRI).Meanwhile, India and China have added numbers to their nuclear arsenals and ‘may occasionally’ have started deploying warheads on high operational alert.India was estimated to have a growing stockpile of about 190 nuclear weapons as of January 2026—a small increase from the previous year. China ‘s stockpile is now 620 warheads from 600 a year earlier, SIPRI said in its annual assessment of the state of armaments, disarmament and international security.On India, the report said, “Nuclear weapons were assigned to a maturing nuclear triad of aircraft, land-based missiles and nuclear-powered submarines (known as SSBNs in Naval parlance)”.SIPRI said more warheads are thought to be in production for additional missiles and that the country’s recent moves have been towards placing missiles in canisters and conducting sea-based deterrence.“Based on this assessment, SIPRI estimates that, as of January 2026, India may have started to deploy a small number of nuclear warheads on a single SSBN conducting occasional deterrence patrols,” the report said.Over the past decade, India’s nuclear planning has increasingly emphasised longer-range weapon systems that appear to be focused on China, but its planning still remains heavily influenced by its long-standing rivalry with Pakistan, SIPRI noted.On Pakistan, the report said Islamabad’s nuclear stockpile remained stable at around 170 warheads as of January 2026. However, it continued to develop its nascent nuclear triad during 2025. While its land- and air-based capabilities are well established, sea-based capabilities remain in the development and testing phase.Pakistan’s development of several new delivery systems and accumulation of fissile material suggest that its nuclear arsenal is likely to expand over the next decade, the report said.Referring to the India-Pakistan skirmish in May last year, SIPRI observed, “Both sides took deliberate steps to keep the conflict at the conventional level and reduce the risk of nuclear crisis”. However, it warned that the clash marked a shift in the region’s dynamics, making the risk of rapid, unexpected escalation to a nuclear level a lingering and serious concern.SIPRI estimated the global nuclear inventory at 12,187 warheads in January 2026. Of these, about 9,745 were in military stockpiles for potential use, while an estimated 4,012 were deployed with missiles and aircraft. Between 2,100 and 2,200 warheads were kept in a state of high operational alert, primarily by Russia and the US.“It is also possible that China and India may occasionally have started to deploy warheads on high operational alert,” the report added. It cited the US Department of Defence as saying that China may now deploy warheads on missiles of a few mobile battalions during peacetime exercises.SIPRI also highlighted developments in Multiple Independently Targetable Re-entry Vehicle (MIRV) technology. China, France, Russia, the UK and the US have long-standing operational MIRV capabilities, while India, Pakistan and North Korea are working to bridge the gap.MIRV technology serves as a powerful ‘force multiplier’ but is widely regarded as one of the most destabilising developments in nuclear strategy because it can overwhelm missile defences and enable quick destruction of multiple high-value military targets, thereby depleting an adversary’s capability to retaliate.India has recently fielded the Agni-V intermediate-range missile with MIRV capability. A test conducted in March 2024 reportedly involved the technology by tracking multiple re-entry vehicles.Meanwhile, Pakistan is developing a medium-range missile, the Ababeel, that can reportedly deliver MIRVs. However, it has performed successfully in only a small number of tests, with more than six years between successive tests. There were also unconfirmed reports that the missile failed in a test launch in August 2025, the report said.