India has made a significant leap in its strategic defense capabilities with the successful test-launch of a K-4 submarine-launched ballistic missile (SLBM) from its second indigenously built nuclear-powered submarine, INS Arighat. This development signals the operationalization of India’s sea leg of nuclear deterrence, marking a critical milestone in its defense strategy. The K-4 missile, with a range of 3,500 kilometers, brings a large swathe of the Chinese mainland within striking range, significantly enhancing India’s strategic reach.
Although the Indian government has refrained from issuing an official statement on the test, aviation authorities issued a Notice to Airmen (NOTAM) advising flights to avoid a 3,490-kilometer corridor in the Bay of Bengal. This corridor aligns with the missile’s declared range, suggesting that India successfully conducted the first underwater launch of the K-4 from an operational nuclear submarine.
Previously, the K-4 had only been test-fired from submersible pontoons, making this a significant step forward in its deployment capability. The INS Arighat, unlike its predecessor INS Arihant, is equipped to carry and launch the long-range K-4 missiles, positioning India closer to achieving credible nuclear deterrence.
INS Arihant, India’s first indigenous nuclear-powered ballistic missile submarine (SSBN), has been instrumental as a technology demonstrator. However, it carries K-15 missiles, which have a range of only 750 kilometers. This range is sufficient for targeting regions in Pakistan but falls drastically short of penetrating deep into Chinese territory.
The introduction of the K-4 missile on INS Arighat remedies this limitation. With a range of 3,500 kilometers, the missile enables India to target strategic locations in China from positions in the Indian Ocean, effectively extending its deterrence posture in the region.
Submarine-based nuclear deterrence is globally recognized as the most survivable leg of the nuclear triad, which also includes land-based missiles and air-delivered nuclear weapons. Nuclear-powered submarines (SSBNs) offer unparalleled stealth and mobility, making them difficult to detect and neutralize, even in a first-strike scenario.
The capability to launch SLBMs like the K-4 ensures that India maintains a secure second-strike capability—essential for credible deterrence. As Dr. Manpreet Sethi of the Center for Air Power Studies aptly notes, “Unless the SLBMs have a range that can help deploy the submarine out of harm’s way, the vessel would not only be constrained for deployment but also become more a liability than an asset.”
By successfully integrating the K-4 missile with INS Arighat, India has taken a crucial step toward securing this survivable deterrent.
The deployment of SLBMs like the K-4 involves overcoming significant technological challenges. These include ensuring missile stability and precision during launch in dual mediums: underwater and atmospheric. The transition from underwater to atmospheric flight requires advanced propulsion systems, guidance mechanisms, and highly stable platforms.
India’s progress in developing an underwater vertical launch system—considered one of the most complex delivery systems in modern warfare—marks a significant achievement for the Indian Navy. With INS Arighat now operational, India has demonstrated its capability to meet these technical demands.
India’s decision to prioritize SSBN development reflects the evolving security dynamics in the Indo-Pacific. The region has witnessed growing Chinese assertiveness, and China is the only other country operating SSBNs in India’s maritime neighborhood. Chinese submarines, including the Jin-class SSBNs, have been sighted in the Indian Ocean, often under the pretext of counter-piracy operations.
However, experts believe that China’s anti-submarine warfare (ASW) capabilities remain underdeveloped. This provides India with a strategic advantage, as its SSBNs can exploit the vastness of the Indian Ocean to remain hidden, ensuring the survivability of its nuclear assets.
India’s SSBN program is poised for significant expansion. The commissioning of INS Aridhaman, the third nuclear-powered submarine, is expected by 2025. INS Aridhaman will also be equipped with K-4 missiles, further bolstering India’s deterrence capabilities. Following this, India plans to introduce two more advanced SSBNs, codenamed S-4 and S-5, armed with the 5,000-kilometer-range K-5 missiles.
A robust SSBN fleet is essential to maintain a credible nuclear deterrent. For effective deterrence, at least one submarine must be on patrol at all times. With multiple submarines, India can ensure continuous patrolling, even when some vessels are undergoing maintenance or refit.
India’s strides in operationalizing its nuclear deterrence come amidst growing debates over its No First Use (NFU) policy. India’s NFU doctrine is built on three pillars: credible minimum deterrence, massive retaliation, and a commitment not to use nuclear weapons first. However, the policy has been criticized for limiting the size and scope of India’s nuclear arsenal.
As China continues to modernize and expand its nuclear capabilities, the disparity between the two countries is becoming increasingly pronounced. Some defense analysts argue that India may need to reevaluate its NFU policy to address this imbalance and maintain strategic stability.
While SSBNs offer unparalleled survivability, they also pose unique operational challenges, particularly in maintaining secure communication with command authorities. SSBNs rely on very low-frequency (VLF) communication systems, which limit the complexity and volume of messages they can receive. This creates the risk of delayed or missed launch orders during a crisis.
India must invest in advanced communication systems to ensure reliable connectivity between its SSBNs and strategic command, addressing potential vulnerabilities in the command-and-control structure.
The test-firing of the K-4 missile from INS Arighat signals a major shift in India’s defense posture. It underscores India’s commitment to developing a credible and survivable nuclear deterrent capable of countering threats from both China and Pakistan.
As tensions in the Indo-Pacific continue to rise, the operationalization of the sea leg of India’s nuclear triad will play a critical role in maintaining regional stability and deterring aggression. By integrating long-range SLBMs into its arsenal, India has taken a decisive step toward ensuring its strategic autonomy and safeguarding its national security interests.
