India tests K-4 missile from nuclear submarine, boosts sea-based deterrence

The K-4 SLBM test from a nuclear submarine strengthens India’s second-strike capability and completes the nuclear triad

December 25, 2025

K-4 missile launch marks major leap in India’s undersea nuclear power

INS Arighaat Test-Fires K-4 Missile in Major Boost to India’s Nuclear Arsenal

India has successfully tested the K-4 submarine-launched ballistic missile (SLBM), marking a significant boost to the country’s sea-based nuclear deterrence. The missile was test-fired from the nuclear-powered submarine INS Arighaat in the Bay of Bengal on Tuesday, with the launch conducted off the coast of Visakhapatnam.

With a strike range of up to 3,500 km, the K-4 dramatically enhances India’s ability to deliver nuclear payloads from beneath the sea. The missile was commissioned into the Indian Navy on August 29, 2024, placing India among a select group of nations capable of launching nuclear weapons from land, air, and underwater platforms.

Derived from the Agni-III land-based ballistic missile, the K-4 is India’s longest-range sea-launched strategic weapon. The missile has been specially adapted for submarine launch, allowing it to eject from underwater silos, breach the ocean surface, and ignite its rocket motor mid-air. It is designed to carry a nuclear warhead weighing up to 2.5 tonnes and can be deployed from Arihant-class nuclear submarines.

As the most concealed component of India’s nuclear triad, the K-4 provides a formidable second-strike capability. Ballistic missile submarines such as the Arihant class operate silently on long deterrence patrols, making them extremely difficult to detect. The “K” series of missiles is named in tribute to former President A.P.J. Abdul Kalam, who played a pivotal role in India’s Integrated Guided Missile Development Programme.

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