Complex sentence: There were three classesbuilt in Czechoslovakia and operated by The Czechoslovak State railway between 1918 and 1989: 354.1 tank engine (originally 629 KKStB class), 387.0 and 399.0 express locomotives.
Split into simpler sentences: There were three classes built in Czechoslovakia and operated by the Czechoslovak State Railway between 1918 and 1989. These were the 354.1 tank engine (originally 629 KKStB class) and the 387.0 and 399.0 classes of express locomotives.