St.Petersburg, 05 November. On 05 November 1967 the first national strategic nuclear submarine cruiser - Pr.667A submarine К-137 Leninets ("The follower of Lenin") - joined the Navy. It was designed by Rubin Design Bureau.

The Soviet Navy had nuclear-powered ballistic submarines (Pr. 658) also designed by Rubin by the time of completing the К-137 construction. However it is the Pr. 667А submarines that are considered to be strategic underwater missile carriers because their firing range became intercontinental. Furthermore the Pr. 658 ships had only three missiles and those of Pr. 667А carried sixteen units (armament has increased more than fivefold).

For the first time pre-launch preparation in the К-137 submarine and follow-on ships of the class took place automatically. In autumn 1969 the second ship of Pr. 667А - submarine К-140 - fired world's first eight-missile salvo.

Pr.667А was equipped with the first domestic automatic battle management system Tucha ("Thundercloud"). It gathered the environmental information, solved navigational tasks, ensured employment of missile and torpedo weapon.

Diving depth of Pr.667А ships (400 meters) was 1.25 times more than that of Pr.658 (320 meters). The submarines of Pr. 667А became the first ships in the world that dived to that depth. To prevent a depth overshoot which can cause an accident, an integrated automatic control system was implemented in the ships of Pr.667А for the first time. Course and speed programmable control as well as hovering was provided.

Compared to Pr. 658 the submarine cruisers of Pr.667А had a higher level of habitability comfort. The entire personnel were accommodated in cabins or crew quarters of non-multiple occupancy. The mess-hall can be easily transformed into a gymnasium or movie theatre.

The construction of 667А submarines commenced in Severodvinsk at Sevmash. К-137 was laid on 4 November 1964 and launched on 11 September 1966. It was commissioned by the Navy on 05 November 1967.

The series was being built relatively fast: the second boat, К-140, was laid on 19 September 1965, launched on 23 August 1967 and introduced into the Navy on 30 December 1967. Totally 34 ships of Pr. 667А were built: 24 in Severodvinsk (from 1967 to 1972) and 10 in Komsomolsk-on-Amur (from 1969 to 1972).

Series 667А was the most numerous among all the projects of Soviet nuclear submarines. Several modifications were developed on the basis of this Project: 667B, 667BD, 667BDR, 667BDRM (four modifications of Delta-class). Ships of the last two types are now in service with the Russian Navy.

"The upgrading possibilities were initially inlaid in the carrier created by General Designer Sergei Kovalev. Hull, systems and power plant turned out to be capable of accepting more and more "charger clips" of more powerful and longer-range missile complexes," - evaluated in his reminiscences Rear-Admiral Vadim Berezovsky, the Commanding Officer of К-137 Leninets and the Hero of the Soviet Union.

From 1967 when the leading ship and the second Pr. 667A SSBN К-140 were delivered to the Navy to 1990 when the last Pr. 667BDRM was accepted by the Navy, 77 submarine cruisers of second generation under five projects (667A, 667B, 667BD, 667BDR and 667BDRM) were built, i. e. on average over three ships a year. The missile weapons have undergone continual improvements - from a single warhead missile with limited flight range up to a MIRV missile of intercontinental range.

"The establishment and development of Pr. 667А SSBNs has set foundation for the system of naval nuclear strategic weapons as a major source of strategic deterrence," - stated Sergei Kovalev, General Designer, in his memoirs.