Despite the extraordinary rescue of Air Force Capt. Scott O'Grady last week, the news out of Bosnia lately has been unrelievedly grim: Just a week before Bosnian Serbs shot down O'Grady's F-16 fighter with a sophisticated SA-6 missile, they had taken several hundred U.N. peacekeepers hostage (many have since been released).

Suddenly, it seemed the bloody Balkan conflict in what used to be Yugoslavia had become more dangerous than ever. Indeed, President Clinton promised to consider sending ground troops on a temporary basis, then amended his words after a congressional uproar. Calling the use of American soldiers "remote, indeed highly unlikely," Clinton promised to deploy them only for the "emergency evacuation" of U.N. troops.

Former U.S. Ambassador to Yugoslavia Warren Zimmermann, who resigned from the State Department in 1994 in part over frustration with U.S. Bosnian policy, thinks almost any action would be better than continued inaction. "The U.S. failure to move led the Serbs to believe they could get away with practically anything they tried," says Zimmermann, 60, now a teacher and senior consultant with the RAND think tank. "And so they tried any-thing, including some of the worst atrocities that have been committed since World War II." At his Great Falls, Va., home, Zimmermann sat down with correspondent Mary Esselman to explain the roots of the conflict and what he thinks should be done.

Why should Americans care what happens in Bosnia? Why not let the various factions fight it out among themselves?

If we do nothing, then the Europeans do nothing, and the Serbs will win. They will take over almost all of Bosnia and make the city of Sarajevo—a city which has stood for ethnic harmony for 500 years—the capital of Serbian Bosnia. They will drive out all the Muslims and Croats in Sarajevo. They will probably execute many of the Serbs they find there, because they consider them traitors. This would be a major defeat for the West, a humiliation for NATO and the U.S.

There's another issue as well. Bosnia, like the U.S., has tried to define itself as a place where people of different ethnic roots can live together. For us to completely stand aside would be to betray our own traditions.

What exactly is the fighting about?

You can capture it in one word: nationalism. In the late 1980s, as the Cold War was ending, Slobodan Milosevic came to power in Serbia on a platform which would have given the Serbs—only 40 percent of the population of Yugoslavia—dominance over the whole country. That was unacceptable to many in four of the five other republics which made up Yugoslavia in 1991. Croatia, Slovenia and Bosnia declared independence. Claiming that all Serbs had the right to live in one state, Milosevic, with the help of the Yugoslav Army, used force against all three breakaway republics.

Is it clear that there are good and bad guys?

There are two clear bad guys: Milosevic and Radovan Karadzic, the civilian leader of the Bosnian Serbs. Nobody needs to worry about moral shadings with them. They are the authors of the policy of "ethnic cleansing" in Bosnia, among other war crimes. The Muslims are the white hats. The hats may have a few smudges on them—they've committed some atrocities of their own—but nothing on the scale of the Serbs. The Croats, led by Franjo Tudjman, are more of a mixture of white and black. They have shown an enormous appetite for breaking up Bosnia so that areas where Croats lived could be annexed to Croatia.

Both the Bush and Clinton Administrations have avoided involvement in Bosnia for fear it could become a Vietnam-like quagmire. Isn't that a legitimate concern?

I think the Vietnam experience is the wrong analogy. The Serbs are not North Vietnamese. For the most part, they're not fanatical fighters who believe very strongly that they're fighting for their homeland. The Serbs embarked on a land grab, and they know that. They comprise less than one-third of the population of Bosnia, and yet they have already taken over two-thirds of the territory. Furthermore, we're not asking the Serbs to get out of Bosnia as we were asking the North Vietnamese to get out of South Vietnam. We're asking them to accept 49 percent of Bosnia. Milosevic has already agreed to the deal. It's the Bosnian Serbs who want more.

Would lifting the arms embargo against the Muslims—as Senate Majority Leader Bob Dole advocates—help even the battlefield?

Lifting the arms embargo would help the Bosnians in the long run, but in the short run the Serbs might be tempted to launch an all-out attack before the Bosnians are trained on the new weapons.

What should the U.S. do?

If we can get the hostages released, then I think a minimal amount of force against Serb military installations could produce an early end to the war and a negotiated settlement. What I have in mind is a strategy of concerted NATO air strikes, not just the one-shot affairs which have gotten us into trouble before. I recognize that to do this would require the U.N. forces either to be better protected than they have been so far or to leave Bosnia. I'm afraid the only language the Bosnian Serbs understand is force.

Will the air strikes be enough?

We don't know for sure. But it seems much worse to do nothing. If the West drops the ball now, with the challenge of the hostages, with the challenge of the American plane being shot down, that will be seen as a major failure. But if the West can find a way to press the Serbs militarily, then I think this testing period could be the key to ending the war.