The FD class was designed and built starting in 1931. These engines were a product of the first Five Year Plan. They were heavy duty workhorse locomotives, and they were widespread across the soviet railway. A respectable 3212 were built, and they were built all the way up until 1942. After the modernization of the soviet railways in the 1950s, a thousand were sent to China, where they were renamed the YouHao (Friendship) class. Unfortunately, the Sino-Soviet split meant that this name was changed to FanXui (Anti Revisionist) and then was finally changed back to FD in 1971. This is not to be confused with the Chinese built QJ class that was renamed FD during the cultural revolution. China sold a few to North Korea, and finally put the locomotives out of service in ‘85.