India advances sea-based nuclear deterrence with K-4 missile test from INS Arighaat

India has successfully test-fired its nuclear-capable K-4 submarine-launched ballistic missile (SLBM) from the nuclear-powered submarine INS Arighaat in the Bay of Bengal.

The test was conducted on Tuesday, December 23, 2025, off the coast of Visakhapatnam and was overseen by the Strategic Forces Command.

According to details reported by The Times of India, the K-4 missile has a strike range of 3,500 kilometres and is designed to carry a two-tonne nuclear payload.

The missile forms a crucial part of India’s sea-based nuclear arsenal and plays a key role in strengthening what is termed the second-strike capability — the ability to respond to a nuclear attack even if land and air platforms are compromised.

There has been no official statement from the Ministry of Defence, but multiple defence officials confirmed the launch to both India Today and The Times of India, characterising it as a major operational step forward.

Developed by the Defence Research and Development Organisation (DRDO), the solid-fuel K-4 missile has undergone several developmental trials in previous years. India Today highlighted that while earlier trials were carried out from submerged test platforms, this launch marks a significant milestone as it was conducted from INS Arighaat itself.

Multiple reports indicate India recently carried out a test launch of the nuclear-capable K-4 submarine-launched ballistic missile from a nuclear powered submarine off the coast of Visakhapatnam, using data from notification here’s a simple missile range map of 3,240-km pic.twitter.com/anyo35GYgB

— Damien Symon (@detresfa_) December 26, 2025

INS Arighaat was commissioned in August 2024 and is India’s second nuclear-powered ballistic missile submarine. It displaces around 6,000 tonnes and is capable of carrying multiple K-4 missiles. The Times of India noted that this is the first known launch of the K-4 missile from INS Arighaat since it entered service.

The test is being viewed as an important step towards fully operationalising India’s sea-based deterrence under its stated nuclear doctrine. A credible undersea capability is essential to maintaining a survivable nuclear arsenal, particularly given India’s declared no first-use policy. The sea leg of this deterrence joins land-based missiles and air-delivered nuclear weapons as part of a three-tier system often referred to as the nuclear triad.

India’s first ballistic missile submarine, INS Arihant, commissioned in 2016, carries the shorter-range K-15 missiles. With the induction of K-4-capable submarines such as INS Arighaat, India moves closer to maintaining a secure and continuous nuclear deterrent beneath the seas.

Future plans include the induction of larger SSBNs capable of carrying next-generation missiles with longer ranges, though timelines have not been publicly confirmed.

What this means – key points:

• The K-4 test confirms India’s ability to launch a long-range nuclear-capable ballistic missile from underwater platforms.
• Submarine-based missiles provide a survivable deterrent, reducing vulnerability to a first strike by adversaries.
• Multiple successful tests and confirmed deployments will be required before full operational readiness is declared.