A SSBN is a military concept and vessel, standing for Submersible Ship Ballistic Nuclear, which is a nuclear-powered submarine designed to carry and launch nuclear-armed Submarine-Launched Ballistic Missiles (SLBMs). The concept originated during the Cold War to create a survivable nuclear deterrent. The world's first operational SSBN was the US Navy's USS George Washington (SSBN-598), which entered service in December 1959 and conducted its first deterrent patrol in November 1960.
The primary problem SSBNs solved was ensuring a nation retained an assured second-strike capability—the ability to retaliate with nuclear weapons even after absorbing a devastating first strike. This mechanism relies on the SSBN's nuclear propulsion, which allows it to remain submerged and undetected for extended periods, maximizing stealth. The missiles are launched from large-diameter vertical tubes while the submarine is submerged. This survivability makes the SSBN the most credible leg of a nation's nuclear triad, which also includes land-based ICBMs and strategic bombers.
For an informed reader, SSBNs connect directly to India's strategic program. India's indigenous SSBNs, such as the INS Arihant, were developed under the Advanced Technology Vessel (ATV) project. These vessels fall under the operational control of the Strategic Forces Command. Recently, India commissioned its third SSBN, the INS Aridhaman (S4), on April 3, 2026. Globally, the US Navy's Ohio-class SSBNs are being replaced by the new Columbia-class SSBNs, which are scheduled to be ready for patrol by October 2030. Furthermore, under the New Strategic Arms Reduction Treaty, US Ohio-class SSBNs had four missile tubes permanently deactivated, reducing their maximum missile capacity from 24 to 20.