India has achieved a significant milestone in its defence capabilities with the successful test of the K-4 ballistic missile, which can deliver nuclear strikes from beneath the sea. The missile was launched from the indigenous nuclear-powered submarine INS Arihant in the Bay of Bengal on December 23, 2025. The test, conducted in strict secrecy by the Defence Research and Development Organisation (DRDO) and the Indian Navy, was initially scheduled for the first week of December but was postponed due to the presence of Chinese reconnaissance vessels in the region, ensuring that the missile’s details remained secure.
The K-4 missile is one of India’s most powerful submarine-launched ballistic missiles, capable of targeting distances up to 3,500 kilometers. This range enables India to strike key regions across Asia from the Indian Ocean, significantly enhancing its strategic deterrence. Weighing 17 tons and measuring 12 meters in length, the missile is designed to carry nuclear warheads weighing up to two tons. It operates on the “cold launch” method, where the missile is first ejected above the water’s surface before its motor engages to propel it towards its target.
With the successful K-4 test, India’s nuclear triad capability is further solidified, allowing it to launch nuclear strikes from land (Agni missiles), air (fighter jets), and now sea (INS Arihant with K-4). This enhances India’s “second-strike” capability, ensuring a robust response to any potential nuclear attack. The successful test marks a critical step in India’s pursuit of self-reliance in nuclear deterrence and its ability to respond to threats with nuclear retaliation, even if the adversary strikes first.