Kronshtadt-class submarine chaser
Project 122bis (NATO codename Kronshtadt class) submarine chasers were a Soviet design which were exported throughout the communist bloc in the 1950s. The first ship, BO-270, was built at Zelenodolsk in 1945-1947 and a total of 227 were built for Soviet Navy (175) and border guard until 1955. As well as this, twenty Project 357 ("Libau" class) despatch vessels were built on the same hull, but were lightly armed. Service history. The ships served in 1950s–1960s on all Soviet fleets and flotillas in the Baltic Sea, Black Sea, Caspian Sea, Arctic Ocean and Pacific Ocean  as part of Soviet coastal anti-submarine defences. Ships were also given to the Soviet Border Guards and were used actively as border patrol ships. Most of the Soviet sub-chasers were decommissioned between 1958 and 1970, although some were in service until the 1990s as training stations. Thirteen of the decommissioned and disarmed ships were delivered to the DOSAAF Voluntary Society for use as training ships. Chinese service history. Two boats of this class, #271 & #274 participated in the Sino-South Vietnamese naval battle in the Paracel Islands on January 19, 1974, with #274 being heavily damaged; however, #274  was able to make it back to the Chinese base at Yongxing Island for emergency repair after the battle, and returned to Hainan Islands the next day. Despite their obsolescence, these boats remained active well into the mid-1990s. Although the ships are no longer capable of venturing into open ocean, these units remain on the People's Liberation Army Navy’s list of its reserve fleet, actively used as weaponry training boats for naval militia in various military maritime districts in China. Additionally, vessels of this class in Chinese service are used to take Chinese children enrolled in military / naval  summer camps and junior military / naval academies for short cruises for patriotic education and public relations missions. Due to the age of these units, however, they are increasingly being used in secondary missions in recent years and according to domestic Chinese media sources, even in this limited capacity, the cruises only consist of short tours within the harbors.