Complex sentence: The club then stayed in Allsvenskan throughout the 1940s and the early 1950s, quite unexpectedly winning its fourth national championship one single point ahead of Helsingborgs IF in the season of 1953/54.
Split into simpler sentences: The club then stayed in Allsvenskan throughout the 1940s and the early 1950s. They quite unexpectedly won their fourth national championship one single point ahead of Helsingborgs IF in the season of 1953/54.