The US Navy's first nuclear deterrent missile

In 1955, the US Navy put into service the SSM-N-8 "Regulus" cruise missile, marking the first time the force possessed nuclear deterrence capabilities, as well as creating the foundation for the later development of the BGM-109 Tomahawk cruise missile, according to WATM.

Initially, the US Navy wanted to improve the performance of the V-1 cruise missile captured from Nazi Germany through the JB-2 Loon project, but it did not bring clear results. By May 1947, the US Army Air Force began developing the MGM-1 Matador cruise missile using a jet engine. The US Navy decided to compete with the Regulus project, which aimed to create a completely new missile capable of being launched from submarines.

By August 1947, the specifications for the Regulus missile were agreed upon, including a 1,400 kg warhead, a range of 930 km, a cruising speed of 1,050 km/h, and a target radius of 4.5 km at maximum range. Testing took place from 1947 to 1953 on the submarines USS Cusk and USS Carbonero. However, the first Regulus prototypes did not have a protective hull, making it impossible for the submarine to submerge before launching the missile.

The completed Regulus version, designated SSM-N-8, was 9.1 m long, had a wingspan of 3 m, a diameter of 1.2 m, and weighed 4.5–5.4 tonnes. Each missile carried a Mk 5 nuclear warhead with a yield of 40 kilotons, equivalent to 40,000 tons of TNT, or a W27 warhead with a yield of two million tons of TNT.

The Regulus missile looks like an F-80 fighter jet but without a cockpit, and the experimental version is also equipped with landing gear for recovery and reuse after each launch. After launch, the missile is guided to its target by two control stations, usually submarines or surface ships equipped with a guidance system, or remotely controlled by a reconnaissance aircraft.

US naval doctrine calls for four Regulus missiles to be available at sea at all times. Initially, the force had to deploy two submarines at a time, the USS Barbero and the USS Tunny, because each could only carry two missiles. Later ships such as the USS Growler, USS Grayback and USS Halibut can carry four to five missiles, allowing them to patrol independently.

Five Regulus-class submarines, based at Pearl Harbor, conducted a total of 40 nuclear deterrence patrols in the North Pacific from October 1959 to July 1964. Their mission was to destroy the Soviet naval base at Petropavlovsk-Kamchatsky in the event of a nuclear war. These were the first deterrence patrols in U.S. naval history, ahead of the Polaris-class ballistic missile submarines.

The upgraded version SSM-N-9 Regulus II was developed in 1958, with a range of 2,200 km and a speed of 2,500 km/h, equipped with a new guidance system with higher accuracy. A total of 48 test launches were conducted, of which 30 were successful, 14 were partially successful and 4 failed. However, the high price of up to 1 million USD/missile, combined with budget pressures and the appearance of the UGM-27 Polaris ballistic missile, caused the Regulus II project to be canceled.

Production of the Regulus missile ended in January 1959 after the 514th missile was produced. At the same time, the Regulus-armed submarines were replaced by the George Washington-class submarines carrying the Polaris ballistic missile. The Regulus series was completely decommissioned in August 1964, with some missiles retained as flying targets for the US Air Force at Eglin Air Force Base.

Although only in service for nine years, Regulus provided the US with a wealth of experience in nuclear deterrence at sea, as well as laying the foundation for the Tomahawk cruise missile line that would follow.