The Project 658M, known to NATO as the Hotel II-class, was the Soviet Union’s first generation of nuclear-powered ballistic missile submarines (SSBNs).
An upgraded version of the original Project 658, the 658M featured improved missile launch systems, allowing it to fire ballistic missiles while submerged.
Entering service during the Cold War, it carried R-21 (SS-N-5 'Sark') missiles, significantly enhancing the USSR’s second-strike nuclear capability.
Though eventually surpassed by more advanced classes, the Project 658M marked a pivotal step in Soviet strategic deterrence and submarine development.