The advent of ballistic-missile submarines during the 1950s immediately prompted the development of a capable helicopter anti-submarine platform capable of operating from the USSR's growing number of surface warships. The result was the Kamov Ka-25 'Hormone' which soon became a fixture of the Soviet navy after initial operation from the Moskva-class helicopter carriers. The Ka-25 is characterized by twin turboshaft engines driving two coaxial contra-rotating propellers, thus eliminating the need for a tail rotor, and features a search radar on a prominent undernose bulge as well as dipping sonar and the ability to carry guided torpedoes. A number were also equipped for the electronic warfare role and as a search and rescue (SAR) or utility helicopter. Foreign users included India, Syria, Vietnam and Yugoslavia while in Russian service it was slowly replaced by the Ka-27.

What began as the Ka-20 'Harp' prototype was first spotted in July 1961 and was later recognized in service as the Ka-25K civil flying crane. The initial ship-based variant was known as the Ka-25BSh 'Hormone-A' while other developments included the Ka-25T 'Hormone-B' electronic warfare helicopter (with the ability to provide target acquisition and mid-course guidance for ship-launched cruise missiles) and the Ka-25PS 'Hormone-C' SAR and utility helicopter which is similar to the Ka-25BSh but with all non-essential equipment removed.