Two successor missiles – the K-5 and K-6 – are reportedly planned for a follow-on class of SSBNs, displacing more than twice that of the Arihant class. The 13,500 ton SSBNs of the so-called S-5 class are to carry twelve of the 5000km range K-5 – development of which started in 2015, with no tests done to date – or a similar number of the 6000km range K-6 which is to have multiple independently targetable re-entry vehicles (MIRVs). It could be safe to suggest that the longer-ranged K-5 could replace the K-4 on the Arihant class to enhance the effectiveness and flexibility of the SSBNs still further.

Just as the Agni series has emerged as the backbone of India’s land-based nuclear deterrent, the K-series is emerging as the principal SLBM series to give India its much sought after nuclear triad. This is no mean achievement and correctly portrayed as a major technological step forward. On the other hand, the Arihant class is a relatively modest vessel by the high standards set by the five larger nuclear powers which operate much more potent vessels. It has to be stated, however, that India is a relative newcomer to the sphere of nuclear-powered submarines and its move to build and deploy an SSBN as its first vessel using such propulsion, is extremely ambitious and despite the inevitable challenges, the vessel is a remarkable achievement. In fact, it might have been expected for India to develop an SSN – like the Akula class submarine currently leased as the INS Chakra. By opting for an SSBN, it is clear India allocated priority to the Arihant project with plans for six SSNs being left for the future.

However, while the INS Arihant does mark an important step forward for India’s nuclear triad, care should be taken not to assume that this leg of the triad is either complete or totally credible. Until the K-4 is operational, the INS Arihant has next to no deterrent capability vs China. In addition, additional SSBNs are needed to allow for continuous patrols. These two necessary steps will take time to come to fruition.