Put up or shut up for UN in Bosnia

A MOMENT of truth is at hand: in the next few weeks the true mettle of the UN in Bosnia will be known. There are several factors - military, political and even meteorological - which are converging to make this the point when the UN must take a more robust line with the local factions - principally the Bosnian Serbs - or get out.

The first factor is the Rapid Reaction Force. Half of this new force will become operational this week, probably next Saturday. The other half - Britain's 24th Airmobile Brigade - has started arriving in Croatia, and should be in place by early August.

Confusion has swirled around the intended role of the force - best illustrated by the farcical coming and going from the title of the word "rapid", which was first applied, then removed, then glued back on again last week.

The 10,000-strong body will comprise about 4,000 British, French, Canadian and Dutch troops, most of whom are already in Bosnia, and 6,000 troops of the British Airmobile Brigade who have started to arrive. The RRF has armed helicopters carrying infantry, suitable for descending swiftly on hilltops and securing commanding positions. It has heavily armoured infantry and engineers able to grind through hostile corridors under heavy fire.

But it is still unclear exactly what the RRF is for. The official line is that it will enable the UN to fulfil its current mandate, without running unacceptable risks. Nor is it there to facilitate the withdrawal of the UN. Last week the French armed forces chief, Admiral Jacques Lanxade, suggested it could be used to create and secure a corridor through to Sarajevo. Other French spokesmen tried to backtrack, saying it would be used to ensure aid convoys got through, but not to create permanent corridors. On Friday, however, President Chirac said that French troops will "guarantee" safe passage on the vital Mount Igman route into Sarajevo if no agreement is reached with the Bosnian Serbs.

It is clear that the RRF is a two-edged sword, able to strengthen the UN in fulfilling its present mandate or, alternatively, shielding it in withdrawal.

What seems certain is that, having amassed this new firepower, Britain and France will no longer be able to continue the status quo, accepting whatever defiance the Bosnian Serbs offer. Attacks on UN forces will no longer be tolerable - nor will the slow starvation before the world's eyes of enclaves like Sarajevo and Bihac. The humiliation for a force of such military might would be so great that withdrawal would be preferable.

The approach of winter will mean any decision on UN withdrawal will need to be made by September. A retreat from Bosnia would take about three months. There are two routes out of central Bosnia. To withdraw in winter conditions would add further horrors to a historic calamity. It is doubtful whether the UN's credibility and authority could survive a winter withdrawal.

The third factor is political. This week the US Senate will vote on a partial lifting of UN Security Council Resolution 713 of September 1991 - the arms embargo against former Yugoslavia. The "Dole Bill", which endeavours to lift the arms embargo against the Muslim-led Bosnian government, but not against the other two warring sides, is expected to pass by a big majority.

There are three considerable obstacles. First, President Clinton is expected to veto it. Then a two-thirds majority vote would be needed to overturn the Presidential veto, which the President could then veto in turn.

Second, the US could not openly supply arms in defiance of a UN resolution. A new resolution would be needed. However, such a one-sided resolution would never get through the UN Security Council, where the Russians have influence, and the embargo would have to be lifted against all sides. Third, even then, the US cannot dictate policy to the UN. But the US is undeniably influential, and if the US Administration endorsed the Senate vote, pressure for the UN to withdraw could increase.

A withdrawal - followed by arms supply - would pose terrific strains in Nato. So if the Rapid Reaction Force proves to be a hollow threat in the theatre of the Bosnian war, the whole trans-Atlantic security relationship is threatened. That is the final - and most important - factor to be calculated in the next six weeks.