Development Project of the Soviet Navy attack submarine 611 (Nat designation Zulu Class) was launched in 1950. The design of the Project 611 diesel submarine was influenced by World War the German Type XXI U-boat. The Project 611 submarine was assembled in Severodvinsk and some parts of the submarine were delivered from Leningrad. A total of 26 ships were built, the first entering service in 1952.
Six submarines of project 611 were converted to become the first ballistic missile submarines. One was armed with a single F-11FM Scud missile and five others with two Scuds each. The missiles were too long to be contained in the hull of the boat, and continued to sail extended. B-67 Soviet submarine successfully launched a missile on September 16, 1955. The success of the Zulus was made to the design of Project 629, the Golf class submarines. In the second half of the 1960 Project 611 submarines were equipped with hydro-acoustic devices and improved navigation and communication systems. They remained in service until the end of the decade of 1980.
