Rail transport in the Soviet Union the Soviet Union collapsed. Twenty other stations were under construction in 1985. The country's rapid transit system was the most intensively used in the world. The Soviet Union was a pioneer in the development of the diesel locomotive to replace the steam locomotive (dieselization) on non-electrified lines. But the USSR failed to make steady progress and while they lead the United States at first, they soon fell behind and their last steam locomotives were retired about 15 years later than for the US. The first mainline diesel locomotive in the world began running in 1924 in the USSR but it
Treaty on the Creation of the USSR Autonomous Soviet Socialist Republic of the RSFSR ceased to exist, and its territory was divided between the new Kazakh and Kirghiz SSRs. In a prelude to World War II, several new republics were created prior to the German invasion of USSR in 1941. The first was the Karelo-Finnish SSR, which on 31 March 1940 was elevated to a union republic from the Karelian ASSR, previously part of the RSFSR. After the annexation of Baltic states, Lithuania, Latvia and Estonia were transformed into the Lithuanian SSR (July 13), Latvian SSR (July 21) and Estonian SSR (also July 21), and were formally