a cross-border operation by the Croatian Army (Hrvatska vojska – HV) 108th Brigade. On 4 April 1992, JNA artillery began shelling Sarajevo. There were other examples of the JNA directly supported the VRS, such as during the capture of Zvornik in early April 1992, when the JNA provided artillery support from Serbia, firing across the Drina River. At the same time, the JNA attempted to defuse the situation and arrange negotiations elsewhere in the country. The JNA and the VRS in Bosnia and Herzegovina faced the Army of the Republic of Bosnia and Herzegovina (Armija Republike Bosne i Hercegovine – ARBiH) and the Croatian Defence Council (Hrvatsko vijeće obrane – HVO), reporting to the Bosniak-dominated central government and the Bosnian Croat leadership respectively, as well as the HV, which occasionally supported HVO operations. In late April 1992, the VRS was able to deploy 200,000 troops, hundreds of tanks, armoured personnel carriers (APCs) and artillery pieces. The HVO and the Croatian Defence Forces (Hrvatske obrambene snage – HOS) could field approximately 25,000 soldiers and a handful of heavy weapons, while the ARBiH was largely unprepared with nearly 100,000 troops, small arms for less than a half of their number and virtually no heavy weapons. Arming of the various forces was hampered by a United Nations (UN) arms embargo that had been introduced in September 1991. By mid-May 1992, when those JNA units which had not been transferred to the VRS withdrew from Bosnia and Herzegovina to the newly declared Federal Republic of Yugoslavia, the VRS controlled approximately 60 percent of Bosnia and Herzegovina. The extent of VRS control was extended to about 70 percent of the country by the end of 1992. Prelude By 1995, the ARBiH and the HVO had developed into better-organised forces employing comparably large numbers of artillery pieces and good defensive fortifications. The VRS was not capable of penetrating their defences even where its forces employed sound military tactics, for instance in the Battle of Orašje in May and June 1995. After recapture of the bulk of the Republic of Serb Krajina (the Croatian Serb-controlled areas of Croatia) in Operation Storm in August 1995, the HV shifted its focus to western Bosnia and Herzegovina. The shift was motivated by a desire to create a security zone along the Croatian border, establish Croatia as a regional power and gain favours with the West by forcing an end to