India has quietly carried out a test of a nuclear-capable submarine-launched ballistic missile (SLBM) in the Bay of Bengal. The test took place on December 23, 2025, but it was not officially announced by the government.
According to sources, the missile tested was the K-4 ballistic missile, which can carry a nuclear warhead. The missile was launched from an Arihant-class nuclear-powered submarine, possibly INS Arihant or INS Arighat.
To keep the test secret, India reportedly canceled a Notice to Airmen (NOTAM) that is usually issued before missile tests. This step was taken because Chinese surveillance ships were present in the region at the time. So far, there has been no official confirmation from the Ministry of Defence, the Defence Research and Development Organisation (DRDO), or the Indian Navy.
Strengthening India’s Nuclear Deterrence
This missile test is an important step in strengthening India’s sea-based nuclear deterrence. With this capability, India ensures a second-strike ability, meaning it can respond with nuclear weapons even if it suffers a nuclear attack first. This makes India’s nuclear defense more secure and reliable.
India’s nuclear forces are based on three platforms, land, air, and sea, known as the nuclear triad. Submarine-based nuclear weapons are considered the most survivable part of this system because submarines can remain hidden underwater for long periods.
Key Features of the K-4 Missile
The K-4 missile is an indigenously developed weapon under India’s K-series of missiles and has been designed by the DRDO specifically for use on nuclear submarines.
Main specifications of the K-4 missile include:
Range: About 3,500 km (some reports say between 3,000 and 4,000 km, depending on the payload)
Length: Around 12 meters
Diameter: Approximately 1.3 meters
Weight: Between 17 and 20 tons
Payload: Up to 2 tons, including a nuclear warhead
Propulsion: Two-stage solid-fuel rocket
Launch method: Underwater cold launch system
Advanced features: Capable of 3D maneuvering and designed to evade ballistic missile defense systems
The K-4 missile is a major improvement over the older K-15 missile, which had a much shorter range of only 750 kilometers. With the K-4, India can target distant locations while keeping its submarines safely far from enemy shores.
Deployment on Arihant-Class Submarines
Each Arihant-class submarine can carry four K-4 missiles. Future nuclear submarines under development are expected to carry up to eight K-4 missiles each, further increasing India’s sea-based strike capability.
The K-4 missile was earlier successfully tested from INS Arighat in November 2024, showing steady progress in India’s submarine missile program.
Although the December 23, 2025 test has not been officially confirmed, it highlights India’s continued efforts to strengthen its strategic nuclear forces. The successful development and testing of the K-4 missile significantly enhanced India’s ability to maintain credible nuclear deterrence and national security.
