India successfully tests second-strike capability with K-4 missile

In a huge milestone, India on Thursday (November 28) successfully tested a K-4 submarine-launched ballistic missile (SLBM) from the indigenously built nuclear submarine, INS Arighaat.

The test validates India’s second-strike capability, reinforcing the credibility of its nuclear deterrence strategy even as rising regional tensions keep the subcontinent on tenterhooks. 'Second-strike capability' refers to the ability to launch a devastating nuclear attack in response, having suffered a nuclear first strike. It's viewed by defence experts as a key component of a country's nuclear deterrence strategy, also essential for maintaining peace.

The K-4 missile, developed by the Defence Research and Development Organisation (DRDO), boasts a range of 3,500 km and can carry nuclear warheads with high precision.

The test is seen as a critical step in operationalising India’s nuclear triad — land, air, and sea-based nuclear delivery systems — which ensures the country’s ability to retaliate even in the face of a devastating first strike.

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A substantial shield 

The success of the K-4 test underscores India’s preparedness for worst-case scenarios, including nuclear conflict. Experts point to the importance of the triad in ensuring stability and deterrence.

For instance, in the hypothetical scenario of an enemy striking first, the nuclear triad ensures that India can strike back. 

Even if major urban centres get destroyed, a robust deployment of India’s nuclear assets — ranging from Agni-series intercontinental ballistic missiles (ICBMs) to submarine-based missiles like the K-4 — could guarantee a retaliatory strike capable of inflicting “massive and unacceptable damage" on the enemy.

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A strategic backbone

Land-based missiles: The Agni-series ICBMs, with ranges exceeding 5,000 km, form the core of India’s land-based nuclear arsenal. These strategic missiles are stationed in hardened silos and mobile platforms, ensuring survivability against a first strike.

Submarine-launched missiles: The K-4 SLBM, launched from INS Arihant and INS Arighaat, provides a stealthy and survivable second-strike capability. Submarines can remain undetected in deep oceans, ready to retaliate at a moment’s notice.

Air-based systems: Strategic bombers such as the Sukhoi-30MKI, Mirage-2000, and Rafale jets are equipped with nuclear-capable missiles and freefall bombs, ensuring flexibility in delivering payloads.

Implications for regional security

The validation of the K-4 missile reinforces India’s nuclear doctrine of "No First Use" while maintaining a credible minimum deterrent. Defence analysts suggest the test sends a clear signal to adversaries, deterring aggression by showcasing India’s ability to respond decisively.

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India conducted its first nuclear test in 1974, becoming the sixth nation to achieve this capability. The exact yield of its nuclear weapons is not publicly disclosed but is estimated to range between 12 and 40 kilotons. While India actively seeks membership in the Nuclear Suppliers Group (NSG), it joined the Missile Technology Control Regime (MTCR) in 2016 and has not signed the Nuclear Non-Proliferation Treaty (NPT) — as it could potentially restrict policy options.

Prime Minister Narendra Modi, who chairs the Nuclear Command Authority (NCA), has reiterated India’s commitment to global nuclear disarmament. Yet, a credible minimum deterrence could present the final Brahmastra that India wields to ward off an expansionist China and a troublesome Pakistan.