The Battlefield 2 total conversion historical realism modification "Battlefield: Korea" deals with the Korean War (1950 - 1953), which is also known as the "Forgotten War".
The Katyusha (BM-13) was a multiple launch rocket system (MLRS) developed in the 1930's with the ZIS-6 soviet truck serving as a platform which utilized the RS-132 aircraft rockets used on the IL-2 Ground-attack plane. This weapons system was used heavily in WW2 and in Korea.
Katyushas (BM-13s) saw action in the Korean War, used by the Chinese People's Volunteer Army against the South and United Nations forces. Soviet BM-13s were known to have been imported to China before the Sino-Soviet split and were operational in the People's Liberation Army.