 The Ustaše began to impose the new laws on the Serb population of the NDH . On 28 May , a group of ten young Ustaše students from the University of Zagreb arrived in Trebinje and began removing signs written in the Cyrillic script used by Serbs . On 1 June , in several towns and villages in eastern Herzegovina , Serbs were shot and businesses belonging to Serb merchants and others were seized . On that day , the Ustaše students in Trebinje shot nine Serbs and arrested another fifteen , apparently due to their links to the inter @-@ war <unk> Association . <unk> began to appear between the brutal treatment of Serbs by the Ustaše and the more careful approach of the other NDH authorities such as the Home Guard , who were aware of the potential danger created by Ustaše methods . In early June , the NDH authorities began operations to confiscate weapons from the population , meeting with immediate resistance . On 1 June , the residents of the village of <unk> <unk> , near Nevesinje , refused to co @-@ operate with weapons collectors . In response , the Ustaše killed a number of Serbs and burned their homes . 
