India has launched its fourth nuclear-powered ballistic missile submarine (SSBN), Aridhaman, as part of its attempt to strengthen its naval fleet. The inauguration ceremony took place this week at the Shipbuilding Centre in Visakhapatnam by Defence Minister Rajnath Singh.

Codenamed as S4, the launch of this submarine marks India’s commitment to strengthen its nuclear deterrence capabilities, particularly on the verge of ongoing diplomatic tensions with Canada. Significantly, the submarine is 75 percent indigenously developed  and is equipped with the K-4 nuclear ballistic missile with a striking range of up to 3,500 km, enhancing India's strategic defence capability.

The S4 is a more advanced version of the second SSBN, INS Arihant, which is equipped with K-15 missiles that has a range of 750 km. INS Arihant was commissioned on August 29, 2024, while the fourth SSBN, INS Aridhaman, is set to be commissioned next year.

On October 9, the Cabinet Committee on Security (CCS) approved the Indian Navy's proposal to build two nuclear-powered attack submarines aimed at deterring potential adversaries in the Indo-Pacific region.
S4 is a part of the growing SSBN fleet and plays an important role in India’s sea-based nuclear capabilities. It can stay underwater for a very long time without needing to refuel. They only need to resupply food, and the crew needs to rest and do maintenance.

India's nuclear submarine fleet is expanding, with INS Arighaat, the third SSBN, now patrolling the deep sea and INS Aridhaman set to join soon. India is also leasing a Russian nuclear submarine to further strengthen its naval power.

The SSBN fleet tends to do deep sea patrolling, strengthening the strategic defence in the Indo-Pacific region. Apart from the SSBN fleet, the Indian government has planned to make more such nuclear-powered attack submarines to counter the challenges in the specific region.

The Indian government is focusing on submarine deterrence, especially nuclear-powered submarines, to counter threats from China. This is because aircraft carriers are vulnerable to Chinese missiles. India is prioritising submarines over a third aircraft carrier. They are also building more conventional submarines to strengthen their naval power.