During World War II, the town was occupied by Axis troops and was included into the Pavelić's Independent State of Croatia (NDH). The fascist Ustashe regime committed the Genocide of the Serbs and the Holocaust. The NDH forces killed in a cruel way more than 600 Serbs in Staro Selo Topusko, while and the largest massacre occurred between 28 July and 3 August 1941 when 250 villagers were executed. Topusko hosted 3rd session of ZAVNOH, the highest governing organ of the anti-fascist movement in Croatia, during which, on May 9, 1944, the Federal State of Croatia was formally founded.