Known in the West by their NATO reporting name as the Juliett class, the Project 651 diesel-electric submarines were designed in the late 1950s to provide the Soviet Navy with a nuclear strike capability against enemy combatants (carriers) and targets along the east coast of the United States. They carried four nuclear-armed cruise missiles, which could be launched while the submarine was surfaced and moving less than four knots (7 km/h). Once surfaced, the first missile could be launched in about five minutes; subsequent missiles would follow within about ten seconds each. Initially, the missiles were the inertially-guided P-5 (NATO reporting name SS-N-3 Shaddock). When submarine-launched ballistic missiles rendered the P-5s obsolescent, they were replaced with the P-6 (also NATO reporting name SS-N-3 Shaddock, though it is a very different missile) and the P-500 4K-80 "Bazalt" (SS-N-12 Sandbox) anti-ship cruise missiles designed to attack American aircraft carriers. A special 10 m2 target guidance radar was built into the forward edge of the sail structure, which opened by rotating. One boat was eventually fitted with the Kasatka satellite downlink for targeting information. The Juliett class had a low magnetic signature austenitic steel double hull, covered by two inch (50 mm) thick black tiles made of sound-absorbing hard rubber. They had exceptionally high reserve buoyancy, and were divided into eight watertight compartments.

PeenemundeTyskland2009VadVar