K-222 was the sole Project 661 "Anchar" (Cyrillic: Анчар) (NATO reporting name: Papa class) nuclear-powered cruise-missile submarine of the Soviet Navy during the Cold War.

The program's objectives were generally satisfied, but the government had failed to include a requirement to minimize the submarine's acoustic signature which meant that K-222 was easily detectable at high speed.

Commissioned in 1969, the-then K-162 was armed with 10 short-range, anti-ship cruise missiles and four torpedo tubes to carry out her mission of destroying American aircraft carriers.

The submarine served in the Soviet Red Banner Northern Fleet through the 1970s, but the discovery of hull cracks led to a lengthy repair period from 1972 to 1975.

The Soviets had some experience with the former, but none with the latter; this proved to be the deciding factor as the committee was unwilling to wait for the lead-bismuth reactor to be developed even though it promised to be smaller for the same amount of power output.

[6] These decisions produced a design that had an underwater speed of 38 knots and was capable of carrying 10–12 missile launchers forward of the sail, but was larger than the specified displacement if fitted with two propeller shafts.

[5] To reduce the technical risk of many of the advanced components chosen, the navy modified five existing submarines to test various systems such as the P-70 Ametist (NATO reporting name: SS-N-7 Starbright), GRAU designation: 4K66; Russian: П-70 «Аметист» 'Amethyst') missiles, sonars and other electronics.

During this 12-hour full-speed test, some of the external hull fittings were ripped off and portions of the grills protecting the water intakes broke loose and were ground up by the water-circulation pumps.

The collapse of the section under hydraulic pressure and the presence of cracks in the welds of both structures revealed that the welders at the Severodvinsk shipyard failed to follow the strict cool down time requirements.

Construction of the submarine was delayed by the delivery of plates for the outer hull by the Kommunar Metallurgical Plant that were contaminated by hydrogen and cracked easily.

About 20 percent of the plates for the outer hull had to be replaced which contributed to the lengthy period that the submarine remained on the slipway before being launched on 21 December 1968.

Shortly afterwards, testing of the submarine revealed that 10 ballast tanks were not watertight despite careful examination and that non-titanium components were not properly isolated from the titanium hull, causing corrosion.

[9][14] Commissioned on 13 December 1969 and assigned to the Soviet Red Banner Northern Fleet, the boat spent most of the next two years conducting sea trials.

During this patrol, the submarine trailed an American battle group centered around the carrier USS Saratoga at high speed as it returned to the United States from the Mediterranean.

[6][15] During this time, the Soviets assessed the possibility of series production of more boats of the class and concluded that the design would have to be modified with longer-range missiles and more torpedoes to improve its combat worthiness.

Although K-222 was not regarded as a successful design, the technology developed for the build enabled the Soviet Union to construct the titanium-hulled Alfa-class and Sierra-class attack submarines.

During the procedure, the entire crew decided to go to lunch ashore on 30 November, violating naval regulations as only shipyard workers remained aboard.

No one was monitoring the core's temperature and the workers only realized that there was a problem when an alarm sounded after a condenser ruptured and radioactive steam and water entered the machinery compartment.