While Serbia and Croatia never declared war on each other, Serbia was directly and indirectly involved in the war through a number of activities. Its foremost involvement entailed material support of the JNA. Following the independence of various republics from SFR Yugoslavia, Serbia provided the bulk of manpower and funding that was channeled to the war effort through Serbian control of the Yugoslav presidency and the federal defense ministry. Serbia actively supported various paramilitary volunteer units from Serbia that were fighting in Croatia. Even though no actual fighting occurred on Serbian or Montenegrin soil, involvement of the two was evident through the maintenance of prison camps in Serbia and Montenegro, which became places where a number of war crimes were committed.