I am in Quetta, Pakistan. Ten minutes ago Fatatoumah Kaba walked up to a group of journalists in the lobby of our hotel and said: "It's happening." She comes from Guinea and has seen the worst of Africa's many humanitarian disasters. But even this veteran of refugee crises was taken aback by the influx across the border.
As I write, the UN is saying that nearly 4,000 Afghan refugees have entered Pakistan at the Chaman crossing about two hours drive from here. It's nearly double the number that came yesterday and they are still coming. The interesting thing is that this is only the number that has come across the main border between the two countries. Nobody knows how many others are coming over on mountain trucks or hidden in the back of smugglers' lorries.
Something terrible is happening on the other side of the border. Where we are, Quetta, is the nearest listening post to the Taliban's spiritual home in Kandahar. But we can only sketch together the vaguest picture of the chaos on the other side. In the space of a few days the area around Kandahar has gone from being the heartland of a brutal and oppressive regime into a zone of terror filled with fleeing civilians. If you've had any experience of refugee problems there is a certain look in the eyes which you quickly recognise. It is a mix of terror, helplessness and pleading. That look is everywhere on the Afghan border right now.
You don't tell these people about big politics or about the war on terrorism. What can we teach them about terror, these anguished thousands who have lived under the tyranny of the Taliban, who have watched their children die of hunger and disease?
While the West is convulsed with worry about anthrax, the Afghans live in the country with the second highest child mortality rate in the world. For more than two decades they have endured and endured and now panic is driving thousands onto the roads.
Reports are filtering in here by the minute. Heavy bombing around Kandahar. Taliban troop concentrations hit. US special forces are on the ground. Things are moving faster than anybody knows. The Taliban ambassador to Pakistan passed through here on his way back from Kandahar about an hour ago and said morale was holding. I don't think anybody believed him. I'd sat behind him on the plane on the journey up to Quetta and he seemed relaxed, singing a religious verse to himself as the plane descended towards the dusty plains of Baluchistan. After five days on the other side of the border he looked distinctly uneasy.
This is unlike any refugee crisis I have ever reported. We are used to seeing the full panoply of Western agencies flooding into disaster zones within days of the first big influx. That is not the case in this most beleaguered of border zones. The agencies are here but they are restricted in where they can go and what they are able to do.
For all the promises of a humanitarian operation to match the war effort, it still looks distinctly limited on this side of the border. In fairness that may have something to do with the fact that Pakistan is already host to two million Afghan refugees, victims of the long civil war. An already poor nation is having to deal with a huge extra burden. That is why the borders are closed and why so many are forced to flee across mountain tracks. But the continuing outflow of refugees makes the closure of borders an unsustainable proposition: both on practical and moral levels.
The most powerless people in the world are fleeing for their lives and they simply cannot be left to fend for themselves. The Allies are correct to point out that it is the Taliban that steals aid and that has refused to allow foreign aid workers to operate in the country. It is also true that in the past few days both the US and Britain have pledged millions in aid to Pakistan. At the moment we are told that sites for refugee camps are ready in areas near the border. But most of the refugees are filtering into the miserable and overcrowded settlements around Quetta. People seek out their relatives or other members of their own ethnic group.
The stories we hear every day in Quetta are heart-rending. You could set out at dawn and record and listen until night and you could do it every day for weeks, and still the stories would still keep coming.
I met Nematallah Popolzoi in the Quetta Hospital. We'd gone there because there were reports of war wounded being brought in. One of them was Nematallah's son, a 10-year-old dark-eyed boy called Said. He had been playing in the market when a bomb struck a Taliban munitions dump. Munitions started to explode and bullets were flying everywhere. One struck Said in the base of the skull. He will live but the bullet cannot be removed from his skull, according to the surgeon.
Said was luckier than the child in the next bed. He was a different kind of war victim. He was injured in a road traffic accident but because he lived in a country with no proper hospitals and no neurosurgeon he had to endure a long agonising journey across potholed roads into Pakistan.
The boy was severely brain damaged and lay with his eyes wide open and terrified, his hands shaking. The doctor told me there were probably thousands like him trapped on the other side of the border. The sick and helpless for whom the arrival of this new war is a blow of unimaginable awfulness.
In another ward a man called Nazir Mohammed sat on a bed surrounded by what appeared to be village elders. He wore a large bandage over his eye and rocked gently back and forth on the bed. It appeared his son was hit in the same explosion, but in this case the flying bullet had killed the five-year-old.
"Only someone who has lost a son can understand what I feel," he said. I have a five-year-old son and I live in dread of ever having to know that feeling. So I was in no position to commiserate or to say anything at all. The grandfather was standing among the men gathered around the bed. "What has my family done to anybody? We never harmed anybody and now I have lost my grandson," he said. As he spoke his voice broke and tears filled his eyes.
These hardy Pathans of the border region are not given to such displays of emotion, particularly in front of strangers. But the old man was beyond worrying about what anybody else might think. The family had run a stall in the bazaar. It was a meagre living, but in Afghanistan it was at least a means of survival. The stall is gone and now so is the child. Nazir Mohammed has lost the world.
The war in Afghanistan has been going on for more than 30 years and tens of thousands have died at the hands of the Taliban and the other warring factions. The misery did not begin with this latest war. However, if we are to accept the pledges that the long-term aim is to bring about a world based on justice, the cause of the refugees should be placed at the top of the international agenda. The next week could see a huge outflow of desperate people across Afghanistan's borders. In the name of humanity our arms should be there to embrace them.
The writer is a BBC Special CorrespondentReuse content