The Hague Tribunal's detention centre is now being filled with senior political and military figures

So far the tribunal has been using its secret - or sealed - indictments as a way of dealing with suspects who would go into hiding if they were publicly charged.

The most prominent figure to have been apprehended by the multi-national S-For peacekeepers was Momcilo Krajisnik, the chairman of the Bosnian Serbs' wartime assembly.

Mr Krajisnik, who was arrested in a surprise raid on his home in April last year, had previously been the closest associate of the one-time Bosnian Serb leader, Radovan Karadzic.

Unresolved questions

Mr Karadzic himself remains in hiding - more than six years after he was publicly indicted for war crimes.

General Mladic: Top suspect still at liberty

In Mrs Plavsic's case a secret indictment was issued against her following Mr Krajisnik's arrest.

It is not clear why no attempt has been made since then to arrest her. Nor has it been explained why she was apparently tipped off about her indictment.

And finally, if she showed a willingness to surrender once she realised she had been charged, it's not easy to understand why her indictment was not then made public - unless there was concern that other suspects might try to prevent her from going to The Hague.

Some of the answers may emerge in due course.

And it is possible that one reason for not subjecting Mrs Plavsic to the indignity of a heavy-handed arrest was to do with the fact that after the war, as President of the Bosnian Serb republic, she turned against Mr Karadzic, Mr Krajisnik and the other hardline nationalists.

Instead she adopted a more pragmatic policy of co-operation with the international community.

Achievement

In spite of that, she has still been charged - for her wartime activities - with genocide, crimes against humanity and war crimes relating to the period just before and during the early phase of the fighting in 1991-92.

The top suspects, including Mr Karadzic and his military commander, General Ratko Mladic, are still at liberty

Although even as nominal vice-president, she was not as much of a key figure during the war as Mr Krajisnik, she was part of the Bosnian Serb hardliners' collective leadership.

She will now be tried alongside Mr Krajisnik.

Putting these two senior figures on trial is a remarkable achievement for The Hague Tribunal which until a couple of years ago found it difficult to place in the dock even the "small fry" among war criminals because most indictees were in hiding.

But thanks, in part, to the secret indictments, the more robust arrest policy of the SFOR peacekeepers and the greater willingness of indictees to surrender themselves, The Hague Tribunal's detention centre is now being filled with senior political and military figures.

'Serbian haven'

Bosnian Croats have always proved more willing to hand themselves over; and one of their wartime generals, Tihomir Blaskic, has already been sentenced to 45 years for a range of war crimes.

Mrs Plavsic will be tried alongside Momcilo Krajisnik

However, the top suspects, including Mr Karadzic and his military commander, General Ratko Mladic, are still at liberty.

The same applies to the former Yugoslav President, Slobodan Milosevic, who - along with four of his senior aides - was indicted for war crimes over Kosovo in 1999.

Indeed, until the new democratic authorities in Belgrade accept their country's commitments towards the UN, Serbia will remain a haven for war crimes suspects.

That will not be acceptable to The Hague Tribunal - however pleased it may be with its increasingly impressive list of detainees.