India's INS Aridhaman, the third Arihant-class nuclear-powered ballistic missile submarine (SSBN), has completed its trials and stands ready for commissioning, significantly enhancing the nation's sea-based nuclear triad.

This 6,700-ton vessel, constructed at Visakhapatnam with over 95 per cent indigenous technology, features an advanced 83 MW pressurised water reactor (PWR) for near-unlimited underwater endurance.​​

The PWR enables INS Aridhaman to remain submerged for up to 90 days, evading detection far better than diesel-electric submarines that require frequent surfacing. This stealth capability is central to India's "No First Use" nuclear doctrine, ensuring survivability against pre-emptive strikes.​

Armament And Strike Reach

INS Aridhaman boasts expanded missile capacity with eight vertical launch system (VLS) tubes, accommodating up to 24 K-15 Sagarika SLBMs (750 km range) or fewer K-4 missiles (over 3,500 km range), all nuclear-capable. These weapons provide flexible second-strike options, targeting adversaries even if land-based assets are neutralised.​​

Future integration of longer-range missiles like K-5 (5,000 km) will further extend its reach, aligning with ongoing DRDO developments. The submarine's design prioritises payload enlargement over predecessors, reinforcing operational lethality.​

Strategic Second-Strike Imperative

As part of India's nuclear triad, INS Aridhaman guarantees retaliation from oceanic depths, rendering first strikes futile. Joining INS Arihant (commissioned 2016) and INS Arighat (2024), it forms a credible trio for continuous deterrence patrols.​

This fleet deters threats from nuclear-armed neighbours, maintaining regional stability through assured massive retaliation. Navy Chief Admiral Dinesh K Tripathi highlighted its role in boosting strike capability and survivability ahead of Navy Day 2025.​

K-4 And K-15 Ranges In Regional Deterrence

India's K-15 Sagarika submarine-launched ballistic missile (SLBM) offers a 750 km range, enabling close-in nuclear retaliation from Arihant-class submarines against regional threats like Pakistan. This limited reach suits tactical deterrence, ensuring second-strike options even if land assets face pre-emptive attack, while keeping submarines near contested waters.​​

The K-4 missile extends this to 3,500 km, allowing launches from safer mid-ocean positions and striking deep into adversary territory, including parts of China. Greater flexibility bolsters survivability, aligning with India's no-first-use policy by guaranteeing massive retaliation.​​

Deterrence Against Neighbours

K-15 primarily counters Pakistan, providing layered sea-based deterrence for short-range scenarios and complicating enemy first-strike calculations. Its deployment on SSBNs ensures underwater survivability, deterring escalation in border conflicts.​​

K-4 shifts dynamics by targeting inland sites across South Asia, prompting Pakistan to accelerate its submarine and missile programs amid perceived threats. This heightens the security dilemma, potentially sparking an arms race while undermining bilateral arms control efforts.​

Strategic Balance

Extended K-4 range enhances credibility against China, enabling strikes from the Bay of Bengal without nearing hostile coasts. Combined with K-15, it forms a robust sea leg of India's nuclear triad, promoting mutual assured destruction (MAD).​​

These missiles fortify regional stability by raising first-strike costs, though they strain Pakistan's resources and complicate Indo-Pacific maritime tensions. Future K-5 integration promises even wider coverage, evolving India's posture.​

Indigenous Advancements And Expansion

Built by Mazagon Dock Shipbuilders Limited and the Directorate for Defence Production, INS Aridhaman exemplifies self-reliance, incorporating advanced stealth and combat systems. Over 95 per cent local content underscores India's progress in nuclear propulsion and submarine engineering.​​

A larger S4* submarine is under construction, with two more S4-class SSBNs slated for induction by 2027, expanding the fleet to five. These developments fortify India's strategic posture amid evolving Indo-Pacific dynamics.​

Based On Republic World Report