During the German invasion of Poland in 1939, Rumia was a site of heavy fighting. It was a flanking position of the main Polish defence line at Kępa Oksywska. Two military cemeteries are located in the area. Soldiers of the 207th Infantry Division (Wehrmacht) and SS members murdered 18 people in Rumia 11–12 September 1939. During World War II, the town was occupied by Nazi Germany, which annexed it to province of Reichsgau Danzig-West Prussia and renamed it to Rahmel. In September and October 1939, SS and SD terrorized ethnic Polish and Jewish population. Most of the victims were either executed at a nearby mass execution site in Piaśnica or sent to Stutthof concentration camp. Approximately half of the pre-war inhabitants of the town were expelled from 1939 to 1941, mostly to the General Government. Many were also deported to forced labour near Szczecin. The town was also a place of internment for several thousand POWs, mostly from the United Kingdom, France and Italy. A forced labour camp and an aircraft assembly plant were located in the town's vicinity. In 1945, shortly before the town's liberation by the Red Army, the local airfield was destroyed by an RAF bombing raid.