The most senior Yugoslav army officer to be charged with war crimes in Bosnia and Croatia went on trial yesterday in The Hague.

General Momcilo Perisic, the former Chief of General Staff of the Yugoslav Army, pleaded not guilty to thirteen charges of war crimes and crimes against humanity, including aiding and abetting the Bosnian Serb siege of Sarajevo, and the Bosnian Serb forces which massacred up to 8,000 Muslim men and boys after the fall of Srebrenica in July 1995.

Although General Perisic, 64, is less well known than Bosnian Serb commander Ratko Mladic, who is wanted for genocide and remains on the run, he was a key figure in the murky relationship between Yugoslavia proper and its armed forces and the Bosnian Serbs, whom Yugoslavia furnished with arms, funds, men and materiel. Without Yugoslavia’s covert support the Bosnian Serb Army would not have been able to carry out its widespread campaigns of ethnic cleansing and murder.

General Perisic’s trial at the UN War Crimes Tribunalis likely to reveal significant details of the connections between the regime of the former Serbian President, Slobodan Milosevic, and forces commanded by the former General Mladic, described in General Perisic’s indictment as his “subordinate”.

Nerma Jelacic, spokeswoman for the tribunal, told The Times: “If you look at the indictment the prosecution is going to try and prove that through General Perisic and his role in the Yugoslav Army Serbia was secretly involved in the wars in Croatia and Bosnia-Herzegovina. It opens the question of the involvement of the Yugoslavia army in the Srebrenica genocide.”

General Perisic’s indictment alleges that he provided significant assistance to the rebel Serbs in both Croatia and Bosnia, by personally establishing two personnel centres within the Yugoslav Army to covertly deploy officers to those two break-away republics and pay their salaries.

In his opening statement prosecutor Mark Harmon cited secret military documents and repeatedly asked the court to go into closed session so he could quote from them. Mr Harmon said that used bullets and shell casings found in Sarajevo and Srebrenica were manufactured in Serbia.

He argued that General Perisic allowed his subordinates to commit war crimes with impunity. “He consistently failed in his duty to investigate and punish war crimes committed by his officers .... of which he was fully aware. He created an environment of impunity wherein his subordinates were encouraged and did persist to commit crimes, knowing there would be no consequences.”

The trial is also set to re-open the controversy over what exactly Western intelligence services — and therefore governments — knew firstly, of the Bosnian Serb preparations for the attack on the besieged enclave of Srebrenica, and secondly the aftermath of its fall, when Bosnian Serb troops carried out the worst atrocity in Europe since 1945.

There have been repeated press reports that Western intelligence services were intercepting conversations between Mr Mladic and General Perisic before the onslaught began, in which General Mladic discussed his plans to attack Srebrenica. This raises the question of why the beleaguered garrison of Dutch UN peacekeepers was not reinforced.

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