I can't get the kaleidoscope of genocide out of my head since my trip last month to the Sudan-Chad border: the fresh graves, especially the extra-small mounds for children; the piles of branches on graves to keep wild animals from digging up corpses; the tales of women being first raped and then branded on the hand to stigmatize them forever; the isolated peasants, unfamiliar with electricity, who suddenly encounter the 21st century as helicopters machine-gun their children.

Then there were the choices faced by the Sudanese refugees I interviewed. For example, who should fetch water from the wells?

The Arab Janjaweed militia, armed by Sudan's government, shoots tribal African men and teenage boys who show up at the wells, and rapes women who go. So parents described an anguished choice: Should they risk their 7- or 8-year-old children by sending them to wells a mile away, knowing that the children have the best prospect of returning?

And what should parents do when the Janjaweed seize their children, or gang-rape their daughters? Should they resist, knowing they will then be shot at once in front of their children?

Or what about the parents described by Human Rights Watch who were allowed by the militia to choose how their children would die: burned alive or shot to death?

Some 1,000 people in Sudan's Darfur region are still dying each week. But at least the world has finally begun to pay attention - and it's striking how a hint of concern in the West has persuaded Sudan to reach a cease-fire there.

President Bush finally found his voice last week, protesting the "atrocities" in Darfur. More forcefully, Kofi Annan warned on the day commemorating the Rwandan genocide that reports about brutalities in Darfur "leave me with a deep sense of foreboding. . . . The international community cannot stand idle."

So far in Darfur, thousands have been killed, and about one million black Africans have been driven from their homes by the lighter-skinned Arabs in the Janjaweed. Vast sections of Darfur, a region the size of France, have been burned and emptied. The Janjaweed have also destroyed wells, or fouled them by dumping corpses into them, to keep villagers from ever returning.

"You can drive for 100 kilometers and see nobody, no civilian," said Dr. Mercedes Tatay, a physician with Doctors Without Borders who has just spent a month in Darfur. "You pass through large villages, completely burned or still burning, and you see nobody."

In the refugee camps in Darfur, malnutrition and measles are claiming the survivors, especially young children. Roger Winter, assistant administrator of the U.S. Agency for International Development, estimates that even if the fighting stops today, at least 100,000 are still likely to die in coming months - of disease, malnutrition and other ailments. Yet Sudan is still curbing access to Darfur by the U.N. and aid groups.

I'm not suggesting an invasion of Sudan. But it's a fallacy to think that just because we can't do everything to stop genocide, we shouldn't do anything. One of the lessons of the last week is how little it took - from Washington, the U.N. and the African Union - to nudge Sudan into accepting a cease-fire and pledging access for humanitarian workers.

Now we need more arm-twisting to get Sudan to comply with the cease-fire (it marked the first day, Monday, by bombing the town of Anka). The Sudanese government is testing us, but so far the State Department has shown a commendable willingness to stand up to it.

We can save many tens of thousands of lives in the coming weeks - but only if Mr. Bush and Mr. Annan speak out more boldly, if the U.N. Security Council insists on humanitarian access to Darfur and if the aid community mounts a huge effort before the rainy season makes roads impassible beginning in late May.

In the last 100 years, the United States has reacted to one genocide after another - Armenians, Jews, Cambodians, Bosnians - by making excuses at the time, and then saying, too late, "Oh, if only we had known!" Well, this time we know what is happening in Darfur: 110,000 refugees have escaped into Chad and testify to the atrocities.

How many more parents will be forced to choose whether their children are shot or burned to death before we get serious?