India Conducts Secret Test of K‑4 Ballistic Missile from Nuclear Submarine in Bay of Bengal

New Delhi: India has successfully conducted a secret test of its powerful K‑4 intermediate-range ballistic missile from the nuclear-powered submarine INS Arighat in the Bay of Bengal, significantly strengthening the sea-based leg of its nuclear deterrence.

The solid-fuel, two-stage K‑4 ballistic missile, capable of striking targets at a distance of up to 3,500 kilometres, was launched from the 6,000‑tonne INS Arighat, India’s second indigenously built nuclear-powered ballistic missile submarine (SSBN). No official statement has been issued by the Ministry of Defence so far.

According to defence sources, the K‑4 missile can carry a two‑tonne nuclear payload and is a crucial component of India’s nuclear triad, which consists of land-based missiles, air-delivered nuclear weapons, and sea-based deterrence systems. The submarine is operated under the Strategic Forces Command, responsible for managing India’s nuclear arsenal.

Sources said a detailed technical analysis will determine whether the test met all predefined parameters and mission objectives. Ballistic missiles, especially submarine-launched systems, typically undergo multiple trials before achieving full operational status.

Multiple Underwater Trials Conducted Earlier

The K‑4 missile was first test-fired from INS Arighat in November last year. Prior to that, several underwater trials were conducted over the years from submerged platforms resembling submersible pontoons. INS Arighat was officially commissioned on August 29 last year, becoming India’s second operational SSBN after INS Arihant.

INS Arihant, commissioned earlier, became fully operational in 2018 but is limited to carrying K‑15 missiles with a range of only 750 kilometres.

Expansion of India’s SSBN Fleet Underway

India is set to commission its third SSBN, INS Aridhaman, in early 2026, followed by a fourth SSBN in 2027–28, under the highly classified Advanced Technology Vessel (ATV) programme, estimated to be worth over ₹90,000 crore. The upcoming submarines will have a larger displacement of around 7,000 tonnes, compared to the first two SSBNs.

Looking further ahead, India plans to develop 13,500‑tonne SSBNs equipped with more powerful 190 MW nuclear reactors, replacing the current 83 MW systems. Despite these advancements, India’s SSBNs are still smaller than those operated by the United States, China, and Russia.

Missile Range to Extend Beyond 6,000 km

Following the operational deployment of the K‑4 missile, India plans to introduce the K‑5 and K‑6 ballistic missiles, with ranges between 5,000 and 6,000 kilometres. These developments are expected to narrow the strategic gap with global nuclear powers that possess intercontinental ballistic missiles (ICBMs).

Most Secure Platform for Retaliatory Strikes

While India’s land-based missiles, led by Agni‑5, and air-delivered nuclear capabilities using fighter jets such as Rafale, Sukhoi‑30MKI, and Mirage‑2000 remain robust, SSBNs provide the most credible deterrence. Under India’s ‘No First Use’ nuclear doctrine, nuclear submarines are considered the safest and most survivable platform for assured retaliatory strikes.

The successful test of the K‑4 missile marks another critical milestone in India’s quest for a reliable, survivable, and credible nuclear deterrent.