after the first world war the prussian state railways, including the eastern railway, along with the other german state railways were incorporated into the newly created deutsche reichsbahn. under the treaty of versailles the polish corridor was created in 1919, separating the free city of danzig and east prussia from germany, leaving east prussia as an exclave. the eastern railway line became a major transit link between east prussia and the rest of germany. this caused a bottleneck at the bridge over the vistula to the south of danzig near dirschau, now tczew under polish control. conflicts over the use of the railway during the interwar period were declared by nazi germany as part of the causes of world war ii.