Complex sentence: In 1952 the USSR produced a derivative of the DUKW adding a rear loading ramp--the Zavod imeni Stalina factory built the BAV 485 on the structure of their ZiS-151 truck.
Split into simpler sentences: In 1952 the Soviet Union produced a derivative of the DUKW, adding a rear loading ramp. The Zavod imeni Stalina factory built the BAV 485 on the structure of their ZiS-151 truck.