From 1936, the Factory in Chrzanów worked at its own cost (without PKP orders) on fast steam locomotive PKP class Pm36 in two versions. Engineer K. Zembrzuski was the contractor of this locomotive. In 1937, the prototype Pm36-1 with aerodynamic lagging won the gold medal on the world exhibition in Paris. The speed test of Pm36 on the back way from Paris reached over on German rails. New railway lines In 1920, a decision was made to construct of new railway line urgently: Łódź–Kutno–Płock–Sierpc–Nasielsk, Kutno–Strzałkowo, and gaps in lines, bypassing the connections broken by the new border with Germany and Gdańsk. A year later, construction began on the Kutno–Konin–Strzałkowo railway, to shorten connections between Warsaw and Poznań. In 1922, construction of the Kutno–Płock and Swarzewo–Hel lines started. In 1924, the Nasielsk–Sierpc line and construction of a new port station and railway junction in Gdynia opened. A Customs War with Germany started in 1925, causing a rush to build a port in Gdynia and a detour line from Silesia to the coast by-passing German territory. In 1927, the first Polish electric railway was built: the private EKD Warszawa–Podkowa Leśna–Grodzisk/Milanówek with branches to Włochy near Warszawa. The French-Polish Rail Association finished construction of the Polish Coal Trunk Line between Bydgoszcz and Gdynia in 1933. In 1934, the beginning of the use of a new railway line, Warszawa–Radom, opening the new connection from Warszawa to Kraków, and preparation to electrification works on Warszawa railway junction and suburbs took place. In 1936 the first electric line based on 3,000 V DC from Warszawa to Otwock and Pruszków opened. World War II On 1 September 1939, railwaymen of Szymankowo stopped a German armoured train before its arrival on the bridge over the Vistula River and blew up the bridge. After the Soviet invasion of eastern Poland on 17 September 1939, most Polish rolling stock fell into Soviet hands. The Polish railways in Silesia, Wielkopolska and Pomorze were adopted by German railways Deutsche Reichsbahn on 25 September. Until the last moment before the German attack on the Soviet Union on 22 June 1941, cargo trains transported goods from the Soviet Union to Germany. Early German attacks on the Soviet Union resulted in Ostbahn possessing railway and rolling stock of PKP with broad gauge track. They began reconstruction to standard gauge. Organized sabotage of railways by the Polish resistance movement in World War II began about the