Wąbrzeźno was invaded by Nazi Germany in September 1939, during World War II, and was occupied by Germany until 1945. The Germans carried out mass arrests of Poles in October 1939. Around 1,000 Poles were arrested and imprisoned, mostly in a temporary concentration camp, established in a local factory, but some also in the local prison. Some of these Poles were murdered in Skrwilno between October 15 and November 15, 1939 and in Nielub on October 17, 1939, while most were murdered in large massacres in Łopatki and Kurkocin (see "Intelligenzaktion"). Nearly 4,000 Polish residents of Wąbrzeźno and the surrounding communities were sent to Nazi concentration camps, established in Potulice and Toruń, and expelled. The Germans banned the use of the Polish language, liquidated Polish schools and organizations, and resettled the town with German colonists, however, the Poles still organized the underground Polish resistance movement.