The 2K12 "Kub" (Russian: 2К12 "Куб"; English: cube) mobile surface-to-air missile system is a Soviet low to medium-level air defence system designed to protect ground forces from air attack. "2К12" is the GRAU designation of the system. Kub is known in the west by its NATO reporting name "Gainful" as well as the US Department of Defense designation SA-6.
Each 2K12 battery consists of a number of similar tracked vehicles, one of which carries the 1S91 (SURN vehicle, NATO designation "Straight Flush") 25 kW G/H band radar (range 75 km/47 miles) equipped with a continuous wave illuminator, in addition to an optical sight. The battery usually also includes 4 triple-missile transporter erector launchers (TELs) and 4 trucks each carrying 3 spare missiles and a crane. TEL is based on a GM-578 chassis, while the 1S91 radar vehicle on a GM-568, all developed and produced by MMZ.
The development of the 2K12 "Kub" was started after 18 July 1958 at the request of the CPSU Central Committee. The system was set the requirements of being able to engage aerial targets flying at speeds of 420–600 m/s at altitudes of 100 m to 7 km at ranges up to 20 km, with a single shot kill probability of at least 0.7.
The systems design was the responsibility of the now Tikhomirov Scientific Research Institute of Instrument Design (NIIP). In addition to NIIP several other design bureaus were involved in the creation of the Kub missile system including the now JSC Metrowagonmash (former MMZ)which designed and produced the chassis of the self-propelled components. Many of the design bureaus would later go on to
co-operate in the development of the successor to the 2K12 "Kub", the 9K37 "Buk"
Kub downed its first ever air target on February 18, 1963 during the state trials at Donguz (Russian: Донгуз) artillery testing range, Orenburg Oblast. It was an Ilyushin Il-28 bomber.
The system entered an extended testing period between 1959 and 1966, after overcoming the technical difficulties of producing the 2K12 "Kub" the system was accepted into service on the 23rd January, 1967 and went into production that same year.
It is sometimes claimed that the M-11 Shtorm (SA-N-3) naval system is a version of the 3M9 but this is not the case, as the M-11 Shtorm is a separate system and, unusually for Russian surface-to-air missiles, has no land-based variant.