Han class

   China began building its submarine force in the 1950s, basing its boats primarily on Soviet designs. However, with the split between Mao Tse Tung and Khrushchev, developments in the 1960s had to be carried out without outside assistance. China lacked the scientific, engineering or technological resources to match the USSR or Western navies, and development of an indigenous nuclear submarine was protracted.

   The first of the Type 91 class attack boats, also known as the Han class, was laid down in 1967. It was commissioned in 1974, but because of continuing problems with the nuclear reactor Submarine 401 was probably not truly operational for a decade. Four more boats were commissioned through the 1980s. The last three are several metres longer, and have vertical launch tubes fitted to allow anti-ship missiles to be carried without cutting into the torpedo load.

   These boats are rather noisy, even by the standards of the time they were built. Their equipment, based on Soviet designs of the 1950s, was primitive. However, the original Soviet ESM system, as well as the ineffective passive sonar, have been replaced by French equipment, and the last three boats have been given an even more extensive refit.

   The primary function of the Han class appears to be anti-surface-ship: the boats carry a mix of straight-running and homing torpedoes, as well as the C-801 Ying-Ji (Eagle Strike) anti-ship missile. They are too noisy to be effective anti-submarine vessels, but they have the capability to strike at shipping lanes far beyond China's coastal waters.

   The next-generation Type 93 SSN is intended to replace the Hans. Being built with Russian help, the design is reportedly based on the Soviet Victor III, which would make it the equivalent of one of the US Navy's Sturgeon-class boats of the 1970s and 1980s. But although the first of the class has been under construction at the Huludao ship yard since 1994, the programme has been considerably delayed.

   As an interim measure, it is believed than the PLA Navy has been looking into the possibility of leasing or buying an Akula class boat from Russia.