RAPE IS OFTEN A TOOL OF WAR, BUT humanitarian observers view the incidence of rape in the Bosnian conflict differently. There is growing speculation - though little hard evidence - that Bosnian Serbs continue to employ systematic rape-as-warfare to ethnically cleanse areas brought under their control. That tactic may have been used again during July's attacks on the so-called safe areas of Zepa and Srebrenica, when the Bosnian Serbs expelled thousands of Muslims from their homes.