 Trifunović-Birčanin and others that were unhappy with the aggressive expansion of the organisation and its move away from traditional Chetnik ideals, and set up the "Association of Old Chetniks" as a rival organisation, but it never challenged the organisation led by Pećanac.In April 1941 the Germans, Italians and Hungarians invaded Yugoslavia leading to the swift collapse of the Yugoslav state and the surrender of the Yugoslav army.Many Serb detachments refused to surrender and took to the hills.