Dear Enemies, Beware! The Silent Giant Ready To Strike – Meet India’s Fourth Arihant-Class Nuclear Submarine | India News

New Delhi: India is said to have taken a major step to bolster its maritime nuclear capabilities with the launch of sea trials for the fourth Arihant-class nuclear-powered ballistic missile submarine (SSBN), which is also called S4. The submarine, as per reports, departed the Shipbuilding Center (SBC) in Visakhapatnam in late November 2025 to embark on a series of trials and evaluations before its formal induction into the Indian Navy.

The new submarine does not have an official name so far. It is reported to weigh about 7,000 tonnes and will be the last Arihant-class submarine before India moves on to the next-generation S5 class. The S4 is built to carry up to eight K-4 ballistic missiles, each able to travel more than 3,500 kilometres. This makes it stronger than the earlier submarines and gives the Indian Navy more powerful strike capability underwater.

One of the most notable features of S4 is its high indigenous content. Reports say that over 80 percent of S4’s equipment and systems are made in India. This is the highest level of Indian-made content in the Arihant program so far. Officials say that this milestone matches the country’s broader goal of achieving technological self-reliance in critical defense areas, particularly in nuclear and naval systems.

With the commissioning of S4, India will have four SSBNs at various stages of service. The first of the class, INS Arihant entered service in 2016 and completed its first deterrent patrol in 2018, while INS Arighaat, which was commissioned in 2024, is already operational. The third submarine, INS Aridhaman, has recently completed its sea trials and is expected to join the fleet in 2026.

S4 itself is projected for commissioning in early 2027. Both Aridhaman and S4 feature an extended hull design, adding roughly 10 meters to accommodate additional K-4 missiles compared with the first two units.

The Arihant-class submarines are equipped with advanced submarine-launched ballistic missiles (SLBMs). Also known as Kalam-4, the K-4 missile can strike targets more than 3,500 kilometers away, carrying a nuclear warhead weighing up to 2,500 kilograms. In parallel, the shorter-range K-15 Sagarika missile has a range of over 750 kilometers and can reach speeds up to Mach 7.5.

Future developments under the program include the K-6 SLBM, which is expected to cover distances up to 8,000 kilometers at hypersonic speeds. It will further strengthen India’s sea-based deterrent and complicate interception by adversaries.

The Arihant program traces its origins to 1984 under the Advanced Technology Vessel (ATV) project, which was conceived to provide India with a credible sea-based nuclear deterrent. The first submarine was launched in 2009, commissioned in 2016. Since then, it has become an important part of India’s nuclear triad, which includes land-based missiles, aircraft and submarines. This setup ensures strong deterrence even if one part of the system is affected.

Looking ahead, the Indian Navy has already begun initial construction work on the S5-class nuclear ballistic missile submarines. These next-generation vessels are expected to displace around 13,500 tonnes, nearly twice the size of the Arihant class. The first S5 units are projected to enter service in the early 2030s.

Plans call for a total of four S5-class submarines by the end of the decade, setting the stage for a formidable underwater strategic capability.

With S4 now in sea trials, India is set to strengthen its position as a top operator of nuclear-powered submarines in the region. The submarine combines Indian-made technology with a strong strategic deterrent at sea.