Introduction

K-4 is an Indian submarine-launched ballistic missile developed for the sea-based leg of India’s nuclear deterrent. It is designed for deployment on Arihant-class nuclear-powered ballistic missile submarines and is a major step beyond the shorter-range K-15 system.

Nature of Missile

• Submarine-launched ballistic missile
• Nuclear-capable strategic missile
• Intermediate-range ballistic missile
• Part of India’s K-series missile family

Developer

• Developed by the Defence Research and Development Organisation
• Manufactured with support from Bharat Dynamics Limited
• Built for India’s strategic sea-based deterrence program

Range

• Commonly reported range is about 3,500 kilometres
• Some public estimates suggest a lower or higher range depending on payload, but for exam use 3,500 km is the safest figure

Launch Platform

K-4 is designed for Arihant-class submarines. Public reporting links it with platforms such as INS Arihant and INS Arighaat, and newer boats in the class are also expected to carry it.

Technical Features

• Two-stage solid-fuel missile
• Length around 12 metres
• Diameter about 1.3 metres
• Weight around 17 tonnes
• Capable of carrying a strategic warhead payload

Development

Public reporting indicates that K-4 was developed as a longer-range follow-on to K-15. It underwent multiple developmental and sea-based tests, and a recent publicly reported test from INS Arighaat in late 2025 highlighted its maturing operational role.

Strategic Role

K-4 is important because it strengthens India’s second-strike capability. A longer-range submarine-launched missile allows Indian SSBNs to remain farther from hostile coasts while still maintaining credible deterrence, making the sea-based nuclear posture more survivable.

Link with Nuclear Triad

India’s nuclear triad has three legs:

• Land-based nuclear missiles
• Air-delivered nuclear weapons
• Sea-based nuclear missiles

K-4 belongs to the sea-based leg and is therefore central to India’s undersea deterrent.

Difference from K-15

K-4 should not be confused with K-15 Sagarika.

• K-15 has a range of about 700 to 750 km
• K-4 has a range of about 3,500 km
• Both are submarine-launched ballistic missiles
• K-4 offers much greater strategic reach than K-15

Significance

• Strengthens India’s sea-based nuclear deterrence
• Increases the credibility of second-strike capability
• Reduces dependence on shorter-range SLBMs
• Improves the strategic value of Arihant-class submarines

Conclusion

K-4 is one of the most important missiles in India’s strategic arsenal because it gives the sea-based deterrent real depth. For exam purposes, remember it as a longer-range, nuclear-capable SLBM of the K-series, developed by DRDO for Arihant-class submarines.