Sierra One, half-an-hour up the road from Sarajevo, has long been notorious in Bosnia as a place where the Serbs regularly shook down aid convoys and reporters passing through. But this time it was an armoured column, and indeed Western policy, that was held at gunpoint - or rather, rendered impotent by mines laid around the wheels of the UN vehicles.
The 15 Swedish and Norwegian troops at Sierra One are the most visible of about 200 UN people now being held throughout Bosnia. Some are under house arrest; some pinned down by mines near the heavy weapons they are guarding. But wherever they are, they have one thing in common.
As became clear when the fighting around Gorazde exploded on Friday, they are all hostages, held against their will, to ward off a repeat of Nato's air attacks on Serbian forces a week ago today.
It is a tactic that seems to have worked. When Lieutenant-General Sir Michael Rose called for further air strikes on Friday to halt the Serbs' advance into the 'safe area' of Gorazde, the main reason that he was overruled by the UN special envoy Yasushi Akashi and the UN Secretary-General Boutros Boutros-Ghali would have been the safety of the hostages. The UN civilian leaders would also have felt obliged to consult all the countries that had UN military observers on Serbian territory.
Across Bosnia, UN soldiers are now being 'treated as enemies', according to the Bosnian Serb leader, Radovan Karadzic. 'After the Nato air strikes, our relations cannot be the same,' wrote Mr Karadzic in a letter to Mr Boutros-Ghali. 'We consider that Unprofor (the UN Protection Force in the former Yugoslavia) is on the Muslim side, and we cannot tolerate that decision. I hope you will understand why we cannot co-operate with Unprofor any more.'
Serbs now say they 'hate and despise' General Rose, who made the Sarajevo ceasefire and oversaw the brilliant Muslim-Croat ceasefire, which has changed central Bosnia outside Serbian control from a war zone into one of peace and hope.
Yesterday the Bosnian Serb Army's deputy leader, General Milan Gvero, said: 'Rose has forfeited his credibility with the Serbian people and the necessary moral, military and political basis for his continued participation in the peace process.'
Western diplomats in Belgrade said General Gvero's tough talk was a virtual ultimatum to the UN that talks would not resume with the British general at the head of Unprofor in Bosnia.
In General Rose's successes, perhaps, lies the cause of the Serbs' paranoia and nervous action. They fear the new federation between the largely Muslim-supported Bosnian government and the Bosnian Croats. Last week, a Bosnian general forecast joint operations and, in the more distant future, perhaps a joint army.
Time is not on the Bosnian Serbs' side. Hence the need to grab one last vital strategic asset - the road through the Gorazde pocket - to keep or use as a bargaining counter.
The UN overcame its long-standing reluctance to use the vast Nato air power at its disposal, and attacked last Sunday, purportedly in defence of its own observers.
The embarrassing failure of one of the bombs to leave its aircraft and two of three that fell not to explode has done the American military no good, in a week that also saw the Americans shooting down two of their own helicopters over northern Iraq. But more worrying to General Rose, the UN commander of 15,000 troops in Bosnia, is the way the situation started falling apart.
The Serbs' reaction was utterly predictable. The 'human shield' idea was well advertised by Saddam Hussein. The Serbs were servicing his aircraft at the beginning of the Gulf crisis, and when sanctions began to pile on Iraq, they even kept a couple. Once the UN's aversion to launching air attacks was overcome, the Serbs realised that one way they could stop them happening again, apart from the intervention of their big Slav brothers, the Russians, was, in the politest way, to take hostages.
Last week, unable to fly into Sarajevo, I headed for Sierra One overland. The troops, from the 'Nordic' battalion, were in good shape. They were reasonably comfortable in their armoured vehicles; one Swedish officer said they were actually rotating the men, so that only the vehicles were hostage. Their main problem, indeed, was that they had run out of toilet paper - but a British lieutenant-colonel from Sarajevo was able to redress this critical deficit.
And even though the Serbs' mines boxed them in, front and back, they were anti-tank mines, which are difficult to set off. The Scandinavians, given their firepower, could quite easily have moved them and driven away. But as children accept punishment at school rather than fight the teacher, because they do not wish to fall foul of the system, so it was agreed that they would remain. It was symbolic of the game being played by the Serbs and the UN: there are unwritten rules, but they are not broken.
Like those interminable prisoner-of-war-camp dramas, there is no reason for gentlemen to be more unpleasant to each other than is necessary, even if, as Mr Karadzic has said, they are technically 'enemies'. A colleague here in Vitez, where the media have been massing after repeated failed attempts to get into Sarajevo, was once arrested by the Serbs. The first day's interrogation began at 8am and was rather formal, but was over by lunchtime; on the second day, out came the slivovitz, and they parted as friends - or at least the Serbs like to think so.
Gorazde may be just another small, nondescript Bosnian town, with the misfortune to straddle a strategic road coveted by the Serbs, but it is also designated a UN 'safe area', and as such is supposedly cloaked in international protection. Its effective capture is graphic proof of Western inability to enforce even a limited defensive shield.
This week's offensive has exploited the flaw in the plan identified by critics when the havens were created in June 1993: guarding Gorazde and the other five UN-protected enclaves - Sarajevo, Tuzla, Srebrenica, Zepa and Bihac - would require 10,000 extra peace-keepers. And, despite repeated appeals from General Rose, they are not coming.
Bosnian officials were aghast that the UN appeared willing to let Gorazde fall. 'The credibility of the United Nations is about zero. It's absolutely outrageous,' said Haris Silajdzic, the Prime Minister.
The Bosnian Serbs, targets of an air assault that was not only limited in scope by design but which actually misfired in practice, would probably agree. No doubt, once they have taken Gorazde, and the highway linking Serbian gains in south-western Bosnia with Serbia proper, they will be disposed to return to the negotiating table.
General Rose has a dilemma: to act against the Serbs and risk further reprisals against UN personnel; or to hold off and leave Gorazde, and 65,000 civilians, to their fates.