India has taken a significant step in strengthening its sea-based nuclear deterrent with the successful test of the K-4 submarine-launched ballistic missile from INS Arighaat in the Bay of Bengal. The launch was carried out off the coast of Visakhapatnam, marking another milestone in India&rsquo;s pursuit of a credible and survivable nuclear triad.
With a strike range of up to 3,500 kilometres, the K-4 considerably enhances India&rsquo;s ability to deliver strategic payloads from beneath the sea. The test brings the missile system closer to full operational readiness and underscores India&rsquo;s growing capability to deploy long-range nuclear weapons from its indigenous nuclear-powered submarines.
Developed by the Defence Research and Development Organisation, the solid-fuel K-4 is derived from the Agni missile series and adapted for underwater launch. It is designed to be fired from submerged submarines using a specialised ejection system, allowing the missile to surface before ignition. Capable of carrying a heavy nuclear payload, the weapon is intended for deployment aboard Arihant-class submarines.
INS Arighaat, commissioned in August 2024, represents the latest addition to India&rsquo;s strategic submarine fleet. Its successful missile test highlights the steady evolution of India&rsquo;s undersea deterrence, narrowing the capability gap with established nuclear powers and reinforcing the most covert and survivable leg of the country&rsquo;s nuclear posture.
&nbsp;

Submarine-launched nuclear-capable missile boosts India’s underwater deterrence

India Tests K-4 Missile at Sea

Submarine-launched nuclear-capable missile boosts India’s underwater deterrence

December 25, 2025 | 18:06 IST