The opening of the first section of the C line on 9 May 1974 was used by the communists as a demonstration of good relations with the USSR, as it was a reference to the liberation of Prague by the Red Army. Three-car trains were put into operation on the C line; the unused part of the stations (because the platforms were designed for five-car trains) was secured with railings. Four-car trains started to run gradually in August 1975.