At the beginning of World War II, in September 1939, German troops invaded Poland towards Mława and Warsaw from the area. In January 1945, the town was taken over by the Red Army from Nazi Germany. Due to the fast Soviet advance, large parts of the populace remained in the town or were overrun on their flight. After World War II the remaining German populace was expelled and the area was assigned to Poland. The Polish Commission for the Determination of Place Names gave it the name of Wielbark, the name by which it had been known in Polish before the war. The Polish name of Wielbark is mentioned in its entry in Geographical Dictionary of the Kingdom of Poland, printed out in the years 1880-1902, in volume XIII published in 1893.