When Bosnia and Herzegovina declared Expressing_publicly independence from Yugoslavia after the 1992 Bosnian independence referendum , the Bosnian Serbs—whose strategic goal was to create Creating a new Bosnian Serb state of Republika Srpska ( RS ) that would include Cause_to_be_included Bosniak-majority areas—encircled Sarajevo with a siege force of 13,000 stationed in the surrounding hills .