India successfully test-fired the K-4 submarine-launched ballistic missile (SLBM) from INS Arighaat, a nuclear-powered ballistic missile submarine (SSBN), in the Bay of Bengal off the Visakhapatnam coast on December 27, 2025. The K-4 is a canister-launched SLBM with a strike range of approximately 3,500 km, capable of carrying a nuclear warhead of up to 2.5 tonnes. Developed by the Defence Research and Development Organisation (DRDO) and manufactured by Bharat Dynamics Limited (BDL), the successful test validated the missile's full operational parameters — including underwater launch mechanics, trajectory, and terminal guidance. INS Arighaat, the second ship of India's Arihant-class SSBN fleet, was commissioned in August 2024. SSBNs are considered the most survivable leg of India's nuclear triad — land-based missiles, aircraft-delivered bombs, and sea-based missiles — because they can remain hidden underwater for extended periods, ensuring a second-strike capability even after a nuclear first strike on India. The K-4 missile significantly extends the range of submarine-based deterrence compared to the K-15 Sagarika (750 km range) already deployed on INS Arihant. With a 3,500 km range, K-4-armed submarines patrolling the Indian Ocean can credibly threaten deep inland targets in adversary territories, strengthening the credibility of India's 'No First Use' (NFU) nuclear doctrine. The test was conducted under the strategic command of the Strategic Forces Command (SFC), which manages India's nuclear arsenal. The development aligns with India's efforts to operationalise a robust nuclear triad — a key component of credible minimum deterrence — as part of its long-term strategic autonomy.
K-4 Submarine-Launched Ballistic Missile Successfully Test-Fired from INS Arighaat in Bay of Bengal: India Strengthens Second-Strike Nuclear Deterrence
India successfully test-fired the K-4 submarine-launched ballistic missile (SLBM) from INS Arighaat, a nuclear-powered ballistic missile submarine (SSBN), in the Bay of Bengal off the Visakhapatnam coast on December 27, 2025. The K-4 is a canister-launched SLBM with a strike range of approximately 3,500 km, capable of carrying a nuclear warhead of up to 2.5 tonnes. Developed by the Defence Research and Development Organisation (DRDO) and manufactured by Bharat Dynamics Limited (BDL), the successful test validated the missile's full operational parameters — including underwater launch mechanics, trajectory, and terminal guidance. INS Arighaat, the second ship of India's Arihant-class SSBN fleet, was commissioned in August 2024. SSBNs are considered the most survivable leg of India's nuclear triad — land-based missiles, aircraft-delivered bombs, and sea-based missiles — because they can remain hidden underwater for extended periods, ensuring a second-strike capability even after a nuclear first strike on India. The K-4 missile significantly extends the range of submarine-based deterrence compared to the K-15 Sagarika (750 km range) already deployed on INS Arihant. With a 3,500 km range, K-4-armed submarines patrolling the Indian Ocean can credibly threaten deep inland targets in adversary territories, strengthening the credibility of India's 'No First Use' (NFU) nuclear doctrine. The test was conducted under the strategic command of the Strategic Forces Command (SFC), which manages India's nuclear arsenal. The development aligns with India's efforts to operationalise a robust nuclear triad — a key component of credible minimum deterrence — as part of its long-term strategic autonomy.
Key facts
- India successfully test-fired the K-4 SLBM from INS Arighaat in the Bay of Bengal on December 27, 2025.
- K-4 has a strike range of approximately 3,500 km and can carry a 2.5-tonne nuclear warhead.
- The missile was developed by DRDO and manufactured by Bharat Dynamics Limited (BDL).
- INS Arighaat is India's second Arihant-class nuclear-powered ballistic missile submarine (SSBN).
- The test strengthens India's second-strike nuclear deterrence capability under the nuclear triad.
- K-4 is a canister-launched submarine-launched ballistic missile using solid propellant.
PYQPrelims/PYQ angle
- RAS 2024 Indigenization in defence production, missile and space technologies — Both concern indigenous missile technology development and its strategic importance for India's defence self-reliance and deterrence posture.
Mains angle
Q: Evaluate the strategic significance of the K-4 submarine-launched ballistic missile's successful test-firing from INS Arighaat for India's nuclear triad and No First Use doctrine.
Answer (50 words):
Test-fired on 27 December 2025 off Visakhapatnam, the DRDO-BDL K-4 is a canister-launched SLBM with a 3,500 km strike range, carrying nuclear warheads up to 2.5 tonnes. Deployed on Arihant-class INS Arighaat, commissioned August 2024, it extends submarine deterrence far beyond K-15 Sagarika's 750 km, credibly reinforcing second-strike capability.
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What is the approximate strike range of India's K-4 submarine-launched ballistic missile?
The K-4 is a submarine-launched ballistic missile developed for India's Arihant-class nuclear submarines. Its commonly reported range is about 3,500 km, much higher than the shorter-range K-15/Sagarika system.
Source: DRDO / DD News / The Hindu / PIB
Frequently asked questions
What is the K-4 missile and what makes it significant for India?
The K-4 is a submarine-launched ballistic missile (SLBM) with a strike range of approximately 3,500 km, capable of carrying a nuclear warhead of up to 2.5 tonnes. It strengthens India's second-strike nuclear deterrence capability, a critical pillar of the nuclear triad alongside land-based and air-delivered weapons.
From which submarine was the K-4 SLBM test-fired, and when?
The K-4 was successfully test-fired from INS Arighaat on December 27, 2025, in the Bay of Bengal off the Visakhapatnam coast. INS Arighaat is India's second Arihant-class nuclear-powered ballistic missile submarine (SSBN).
Which organisations developed and manufactured the K-4 missile?
The K-4 SLBM was developed by the Defence Research and Development Organisation (DRDO) and manufactured by Bharat Dynamics Limited (BDL). It uses solid propellant and is launched from a canister.
What is a nuclear triad and how does the K-4 test relate to it?
A nuclear triad refers to a three-pronged nuclear delivery capability — land-based ballistic missiles, air-delivered bombs, and submarine-launched missiles. The successful K-4 test from INS Arighaat reinforces the sea-based leg of India's nuclear triad, ensuring credible second-strike capability even after absorbing a first strike.
What is an SSBN and why is INS Arighaat important for India's strategic forces?
SSBN stands for nuclear-powered ballistic missile submarine, which can remain hidden underwater for extended periods and launch nuclear missiles covertly. INS Arighaat is India's second Arihant-class SSBN, expanding the operational fleet and making India's sea-based nuclear deterrent more robust and credible.
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