By NICHOLAS D. KRISTOF – New York Times.

This may be a first for the Arab world: An American airman who bailed out over Libya was rescued from his hiding place in a sheep pen by villagers who hugged him, served him juice and thanked him effusively for bombing their country.

Even though some villagers were hit by American shrapnel, one gamely told an Associated Press reporter that he bore no grudges. Then, on Wednesday in Benghazi, the major city in eastern Libya whose streets would almost certainly be running with blood now if it weren’t for the American-led military intervention, residents held a “thank you rally.” They wanted to express gratitude to coalition forces for helping save their lives.

Doubts are reverberating across America about the military intervention in Libya. Those questions are legitimate, and the uncertainties are huge. But let’s not forget that a humanitarian catastrophe has been averted for now and that this intervention looks much less like the 2003 invasion of Iraq than the successful 1991 gulf war to rescue Kuwait from Iraqi military occupation.

This is also one of the few times in history when outside forces have intervened militarily to save the lives of citizens from their government. More commonly, we wring our hands for years as victims are massacred, and then, when it is too late, earnestly declare: “Never again.”

In 2005, the United Nations approved a new doctrine called the “responsibility to protect,” nicknamed R2P, declaring that world powers have the right and obligation to intervene when a dictator devours his people. The Libyan intervention is putting teeth into that fledgling concept, and here’s one definition of progress: The world took three-and-a-half years to respond forcefully to the slaughter in Bosnia, and about three-and-a-half weeks to respond in Libya.

Granted, intervention will be inconsistent. We’re more likely to intervene where there are also oil or security interests at stake. But just as it’s worthwhile to feed some starving children even if we can’t reach them all, it’s worth preventing some massacres or genocides even if we can’t intervene every time.

I opposed the 2003 Iraq invasion because my reporting convinced me that most Iraqis hated Saddam Hussein but didn’t want American forces intruding on their soil. This time my reporting persuades me that most Libyans welcome outside intervention.

“Opinion was unanimous,” Michel Gabaudan, the president of Refugees International, told me on Wednesday after a visit to Libya. Mr. Gabaudan said that every Libyan he spoke to agreed that the military strikes had averted “a major humanitarian disaster.”

“Men, women and children, they are ecstatic about the role of the coalition but worried that it may not continue,” he said.

Some Congressional critics complain that President Obama should have consulted Congress more thoroughly. Fair enough. But remember that the intervention was almost too late because forces loyal to Col. Muammar el-Qaddafi were already in Benghazi. Indeed, there was a firefight on Sunday right outside the hotel in Benghazi where foreign journalists are staying. A couple of days of dutiful consultation would have resulted in a bloodbath and, perhaps, the collapse of the rebel government.

Just before the airstrikes, Libyans were crossing the border into Egypt at seven times the normal rate. Once the strikes began, the exodus ended and the flow reversed. For all the concern about civilian casualties, Libyans are voting with their feet — going toward the airstrikes because they feel safer thanks to them.

Critics of the intervention make valid arguments. It’s true that there are enormous uncertainties: Can the rebels now topple Colonel Qaddafi? What’s the exit strategy? How much will this cost?

But weighed against those uncertainties are a few certainties: If not for this intervention, Libyan civilians would be dying on a huge scale; Colonel Qaddafi’s family would be locked in place for years; and the message would have gone out to all dictators that ruthlessness works.

The momentum has reversed. More airstrikes on Colonel Qaddafi’s artillery and armor will help. So would jamming his radio and television broadcasts. Arab countries are already delivering weapons and ammunition to the rebels, boosting their capabilities and morale. In short, there are risks ahead but also opportunities.

A senior White House official says that the humanitarian argument was decisive for President Obama: “The president was chilled by what would happen to the people of Benghazi and Tobruk. There were critical national security and national interest reasons to do this, but what compelled the president to act so quickly was the immediate prospect of mass atrocities against the people of Benghazi and the east. He was well aware of the risks of military action, but he also feared the costs of inaction.”

I’ve seen war up close, and I detest it. But there are things I’ve seen that are even worse — such as the systematic slaughter of civilians as the world turns a blind eye. Thank God that isn’t happening this time.