The Army of Republika Srpska was newly established and put under the command of General Ratko Mladić, in a new phase of the war. Shellings on Sarajevo on 24, 26, 28 and 29 May were attributed to Mladić by UN Secretary-General Boutros Boutros-Ghali. Civilian casualties of a 27 May shelling of the city led to Western intervention, in the form of sanctions imposed on 30 May through UNSCR 757. That same day Bosnian forces attacked the JNA barracks in the city, which was followed by heavy shelling. On 5 and 6 June the last JNA personnel left the city during heavy street fighting and shelling. The 20 June cease-fire, executed in order for UN takeover of the Sarajevo airport for humanitarian flights, was broken as both sides battled for control of the territory between the city and airport. The airport crisis led to Boutros-Ghali's ultimatum on 26 June, that the Serbs stop attacks on the city, allow the UN to take control of the airport, and place their heavy weapons under UN supervision. Meanwhile, media reported that Bush considered the use of force in Bosnia. World public opinion was 'decisively and permanently against the Serbs' following media reports on the sniping and shelling of Sarajevo.