After World War I, the rivalry calmed, and Gothenburg supporters became known as friendly and sportsmanlike fans. However, this only applied to the behaviour on home ground, as IFK supporters continued to behave badly when travelling to away matches by train (called "Göteborgstågen", the Gothenburg trains), a phenomenon that grew quickly in the 1920s. This behaviour peaked in 1939, just after the outbreak of World War II, when approximately 1,900 IFK fans travelled to Borås to see IFK play Elfsborg. After a 2–3 loss, the fans fought with the Borås police, before returning home to Gothenburg and disturbing a wartime blackout exercise.