The prisoner has only just been taken into custody. Ahead of him a trial for genocide and crimes against humanity in front of an international criminal court. I have watched and waited for this moment for years. In truth I never believed it would happen. Yet now that it has come I feel no elation, only a sense of deep sadness. I wonder what Valentina made of the news, or Flora or the boy they call "Grenade". Was there cheering across the hillside like they always said there would be? Perhaps the only place to appreciate the power of what has happened is at the scene of the crime itself, and for me that is not an option right now.
The man whose crimes I witnessed and whose name I can never forget is a prisoner of a new world justice. What is it like for that bringer of death to sit in a United Nations prison cell, stripped of his power? We've had the laws to bring men like him to court for decades but only lately, shamefully and appallingly lately, have we decided to take action. So for every butchered innocent whose corpse I saw in the fields and hills, the ruined houses and churches I salute the law that has brought Sylvestre Gacumbitsi to justice. Oh, and of course Slobodan Milosevic, too.
They were both arrested this week. One in a great blaze of publicity, the other quietly in a remote African town. One was the Serbian dictator who unleashed the most savage campaign of ethnic slaughter Europe had witnessed since the Second World War, the other a Rwandan mayor who personally supervised the murder of thousands of people. The worst of men, these two, the worst of humanity.
In the charges read to Gacumbitsi, prefect of the commune of Rusomo, it was alleged that he had personally stabbed a pregnant Tutsi woman and dragged the foetus from her body. I was not surprised by the charge. For seven years I have been travelling to the village of Nyarubuye, near Rusomo, where Gacumbitsi ordered the murder of the entire Tutsi community. I have recorded interviews and followed the progress of the survivors and in every conversation the name of Gacumbitsi has hovered like a malign shadow.
I saw the work of Milosevic, too. I stood in a courtyard in Bosnia while the survivors of Arkan's attack on Zvornik queued alongside scores of bodies recovered from a mass grave. The survivors howled and fainted at the ghastly mulch of ruined humanity spread out before us on that spring morning. They had come to try to identify loved ones and occasionally a name would be shouted, "Mustapha" or "Ahmed" as some face was half recognised amid the decomposing corpses. I wanted so badly that morning to drag Milosevic and his wolves in among the stinking dead, to bury their faces in that horror so that it would cling to them for all eternity.
Looking at the last decade of the 20th century and the barbarous convulsions of Rwanda and the former Yugoslavia, I've struggled to believe that any lessons have been learnt or anything gained. In 1945 we pledged to respect the rights obliterated by the Nazis. But "never again" became the most broken promise of our age. Political and military leaders ignored the Geneva conventions and killed the innocent with impunity. The Americans did it in Vietnam, the Russians in Afghanistan, the Indonesians in East Timor and Pol Pot in Cambodia. And they are but a few of many examples. So much, you might think, for the law of war and the responsibility of leaders.
But if some cynicism is justified, despair is definitely not. Something very profound has happened in the past decade, a movement so significant that it will register among the greatest achievements in the history of humanity. The horrors of Yugoslavia and Rwanda have forced the world to accept that leaders should be made accountable for the orders they give; the myth that genocide and war crimes are merely the consequence of atavistic hatred has been exploded. Ever since Nuremburg the law has said war crimes are the responsibility of political and military leaders. But with this week's arrests the law at last showed it had teeth.
Going after the little fish is easy. No one cares much if some African peasants are rounded up and stuck in jail for killing their neighbours, or if some Bosnian Serb warlord is snatched off the streets by the SAS. But seeing Milosevic in The Hague should send the most emphatic message to the abusers of human rights everywhere. This will be dependent on a major change of attitude on the part of the US. The country that slapped itself on the back for getting Milosevic to The Hague supported the murderous campaign of territorial redemption waged by Croatia's Franjo Tudjman in the Krajina. The late Mr Tudjman would have been a worthy candidate for indictment but his American friends would surely have resisted the move.
Nor can we confidently talk of a new international justice while America refuses to ratify the treaty to set up a permanent International Criminal Court. In short the US thinks it is fine to send the leaders of dodgy Third World regimes and Balkan dictators for international trial but God forbid that an American officer might one day be called to account. It is a sickening example of double standards. As Judge Richard Goldstone, the former UN Chief Prosecutor, pointed out this week, it is a policy dictated by the military. That's right: American democracy is being railroaded by soldiers.
But Judge Goldstone is not pessimistic. In a Human Rights Watch lecture in London this week he spoke of the international community of conscience that would continue to push war crimes prosecutions. Look at the storm kicked up about Senator Bob Kerrey, a former US presidential candidate, who is being asked to explain the killing of Vietnamese villagers 30 years ago, or the controversy in France over the torture and murder of prisoners in Algeria.
In Chile the prosecution of Pinochet would have been unimaginable had it not been for the willingness of European judges and police to arrest him in the first place. The decision of the House of Lords in the Pinochet case created a climate in which the inconceivable became the inevitable.
We should all be outraged that criminals roam free after so much blood has been shed. Some are protected by powerful friends (like Mengistu, the dictator of Ethiopia, living in Zimbabwe), others scream angry denials and ignore the abundant evidence, others indulge in self-righteous posturing, apparently astounded that their names would be mentioned in the same breath as war crimes. But we know who you are. The dead may have vanished into dust but there are witnesses and documents, and history has recorded your deeds. Not all the war criminals of our time will face justice, but there is an exquisite pleasure in the thought that they now have something serious to worry about.
The world is full of re-invented men who look at you and say: that was a war, I did what I had to do. It is different now. Goodbye to the past. The arrests of Milosevic and Gacumbitsi – men from other worlds but brothers in blood – show that maybe you can't just don a new face and fool the world, or at any rate not all of the world. At the very worst our new justice means that many of the old killers will have to alter their travel plans. At best we will be able to say to the victims: here at last is justice.
The writer is a BBC Special CorrespondentReuse content