Key Point: This submarine fiasco shows the limits of Soviet technology.
The Cold War saw numerous submarine accidents, especially on the Soviet side. For much of its existence, the USSR tried to maintain a world-beating military with a second-rate economy. Throughout the era, the Soviets struggled to maintain their magnificent weapons of war. In the effort to close this gap, the crews of Soviet submarines often paid with their lives.
But only one submarine had the poor luck to sink twice.
The Charlie class (Project 670) was the third class of cruise-missile submarines (SSG) deployed by the Soviet Union, and the second to use nuclear propulsion (SSGN). The Soviet Navy expected to use early SSGs and SSGNs to attack American land targets, primarily cities and naval bases, with conventional and nuclear warheads. The cruise missiles of the time lacked sophisticated guidance mechanisms, making attacks against the interior impossible. Over time, the improvement of radar-homing technology (as well as improvements in ballistic-missile technology) allowed the Soviets to reconceptualize the use of cruise missiles. The Echo II class, the immediate predecessor to the Charlies, were built with an anti-shipping role in mind. Antiship missiles appealed to the Soviets because of the noise of their submarines; the Soviet Navy did not expect that its boats could close within sufficient range to hit American capital ships with torpedoes.
Designed in the early 1960s, the first Charlie entered service in late 1967. Displacing 4900 tons and capable of twenty-four knots, the Project 670 submarines fired the P-70, a subsonic missile which could deliver a conventional warhead or a two-hundred-kiloton nuclear device up to thirty-five miles. This was not a particularly long distance, almost certainly within the anti-submarine warfare (ASW) reach of a carrier battle group or other major NATO asset, but development problems with a new missile forced the design choice. In any case, the ability of the Project 670 boats to fire while underwater gave NATO planners new headaches.