Kammala jumla mai zuwa: Bayan mamayewar Nazi Jamus da Soviet na Poland, wanda ya fara Yaƙin Duniya na II, Kolno ya mallaki sojojin Jamus a ranar 8 ga Satumba, 1939. A ranar 12 zuwa 13 ga Satumba, 1939, "Einsatzgruppe V" na Jamus ya shiga garin don aikata laifuka daban-daban a kan jama'a. A ranar 29 ga Satumba Soviets sun shiga yankin daidai da Yarjejeniyar Ribbentrop-Molotov. Soviets sun aiwatar da ƙauracewar jama'a na mazauna zuwa Tarayyar Soviet. Tuni a cikin 1939, Stanisław Milewski ya shirya ƙungiyar juriya ta Poland a Kolno. Garin ya kasance a karkashin
Harkokin Soviet har zuwa Operation Barbarossa (22 ga Yuni 1941) lokacin da Wehrmacht ya sake mamaye shi.