 According to the Yugoslav census of 1931 , the population of eastern Herzegovina comprised 4 per cent Croats , 28 per cent Muslims , and 68 per cent Serbs . According to Professor <unk> Tomasevich , the estimated population of the districts of Bileća , Gacko and Nevesinje was only around 1 @.@ 1 per cent Croat , so in those areas nearly all the NDH government appointments and local Ustaše units were staffed by Muslims , an ethnic group that made up about 23 @.@ 7 per cent of the local population . The poor Muslim peasants of eastern Herzegovina largely sided with the Ustaše . The NDH government immediately tried to strengthen their position by <unk> the Serbs , who , according to Tomasevich , comprised around 75 per cent of the population . 
