India’s successful test of the K-4 intermediate-range ballistic missile from INS Arighaat in the Bay of Bengal on 23 December 2025 marks a qualitative shift in its nuclear deterrent posture.

The test validated the full integration of the missile, submarine and command-and-control architecture, moving India’s sea-based deterrent from a largely developmental phase to one that is operationally credible. 

With an approximate range of 3,500 kilometres, the K-4 substantially extends India’s second-strike reach, allowing targeting flexibility deep into the Indo-Pacific while keeping launch platforms in relatively secure bastions.

Official briefings around the test were deliberately low-key, underscoring continuity rather than escalation. Defence officials characterised the launch as a routine exercise focused on readiness and reliability rather than as a response to any specific contingency. This carefully calibrated public messaging tied the development explicitly to India’s long-standing No First Use policy, projecting the K-4 not as an instrument of coercive signalling, but as a measure to reinforce assured retaliation and the credibility of India’s nuclear doctrine.

The most notable strategic implication lies in the geographic rebalancing of India’s deterrence posture from the western land front to the eastern maritime theatre. Historically, Indian strategic planning concentrated on continental threats, with the Bay of Bengal perceived primarily as a commercial and connectivity space.

The 1971 Bangladesh Liberation War, however, exposed the vulnerability of this assumption when the deployment of the USS Enterprise to the Bay highlighted how extra-regional powers could exert pressure from the sea despite an advantageous situation on land. That episode catalysed a gradual but decisive reassessment of the Bay of Bengal as a critical strategic zone.

In subsequent decades, the Bay of Bengal has increasingly become a theatre of great-power competition and undersea activity. Chinese naval survey ships, intelligence-gathering vessels and submarines have appeared with mounting frequency, often under the guise of research or goodwill missions.

Reports such as the sighting of a Chinese research vessel allegedly operating with its Automatic Identification System switched off near Indian waters have heightened Indian concerns over covert mapping of the seabed, surveillance and possible preparation of undersea operating areas.

The People’s Liberation Army Navy has also expanded its operational footprint through flotillas transiting the Andaman Sea and skirting the Bay of Bengal. These deployments, typically couched in benign terms like search-and-rescue drills or escort training exercises under banners such as ‘Peace and Friendship 2025’, nonetheless convey a steady normalisation of Chinese naval presence in proximity to India’s eastern maritime approaches.

Such activity contributes to an evolving pattern in which the Bay of Bengal is no longer a peripheral body of water, but an active arena for strategic signalling and presence operations.

Regional instability further compounds the changing maritime security environment. The Coco Islands, located close to India’s Andaman and Nicobar archipelago, have reportedly seen upgraded airstrips, jetties and communications infrastructure, amid China’s deepening involvement in conflict-ridden Myanmar.

The Kyaukphyu Port project and associated energy corridors from the Bay of Bengal to China’s Yunnan province effectively convert the bay into an access gateway to the Chinese hinterland, enhancing Beijing’s stakes in the area’s security and its motivation to maintain a sustained presence.

Bangladesh’s military modernisation under its Forces Goal 2030, particularly the induction of two Chinese-origin submarines and the construction of the BNS Pekua submarine base with Chinese assistance, injects an additional layer of complexity.

While framed as part of Dhaka’s legitimate defence development, these moves signal more entrenched Sino–Bangladeshi defence cooperation, including training and technical support, which in turn creates potential avenues for Chinese operational familiarity with the Bay of Bengal’s undersea environment. For India, this reinforces the perception of an encroaching Chinese maritime and undersea footprint along its eastern periphery.

Domestic political flux and governance challenges in both Bangladesh and Myanmar increase the likelihood that external powers will seek and secure more durable strategic footholds. Allegations by former Bangladeshi prime minister Sheikh Hasina that the United States exerted pressure over St Martin’s Island to secure basing rights, and her subsequent claims that the current interim leadership is placing national sovereignty at risk, highlight the island’s emerging significance. Control over St Martin’s would offer any external power enhanced surveillance and operational oversight of the Bay of Bengal’s northern approaches, amplifying its strategic relevance.

Against this backdrop, India’s Eastern Naval Command has seen its remit expand from primarily coastal defence and limited sea control to managing a complex theatre of great-power naval presence, regional submarine proliferation and undersea competition.

The decision to base India’s ballistic missile submarine fleet on the eastern seaboard, using the Bay of Bengal as a principal operating area, is therefore a product of strategic design rather than convenience. The bay now functions not only as a test range, but as an active deterrence bastion hosting a key leg of India’s nuclear triad.

The deployment of K-4-armed SSBNs from the Bay of Bengal fundamentally recalibrates India’s deterrence geometry. By enabling secure second-strike capabilities from relatively protected eastern bastions, India reduces its dependence on land-based and western-facing assets and introduces a distributed, less vulnerable deterrent posture.

This maritime nuclear presence enhances survivability, complicates adversary targeting and underlines India’s transition from a predominantly land-centric nuclear strategy to one anchored in flexible, sea-based retaliation.

At the doctrinal level, these changes do not amount to a formal shift in stated principles, which remain anchored in No First Use and credible minimum deterrence. Instead, the evolution lies in posture and deployment: quiet consolidation of undersea nuclear capabilities, increased reliance on the eastern maritime theatre and a measured response to the multipolar competition unfolding in the Bay of Bengal. 

What began in 1971 as a moment of perceived vulnerability to naval coercion has now matured into a posture of understated confidence, grounded in an operationally viable, sea-based deterrent arrayed from India’s eastern seaboard.

IDN (With Agency Inputs)