Until Aug. 2, when the prospect of war set nerve ends vibrating throughout Washington, William M. Baker managed five of the FBI's six major criminal investigative programs and spent the greatest time on cases involving savings and loan fraud, drugs and organized crime.

Suddenly all that changed. The program in his purview that had received the smallest amount of bureau resources and the least of his personal attention instantly became of paramount national importance -- counter-terrorism.

Last night that new, overriding priority of Baker's culminated in perhaps the tightest security net in Washington's history. It also provided a glimpse into a battle that takes place mainly out of sight and poses a democratic dilemma as old as the Republic.

Assembled in one chamber for President Bush's State of the Union address was virtually the entire leadership of the U.S. government at a time when the nation is at war and faces open threat of terrorist retaliation. The conflict is over how to safeguard America's freedoms while imposing tightened security restrictions that limit them. Lincoln framed that dilemma best during the Civil War. "Must a government of necessity be too strong for the liberties of its people," he asked, "or too weak to maintain its own existence?"

From his office in the fortress-like bunker at FBI headquarters, Baker has been dealing virtually around the clock with both sides of those related problems. As head of the bureau's criminal investigative division, he has the job of point man on the domestic terrorist front, a role that now has him spending his days in briefings at the White House and Congress, meetings with his counterparts at the Central Intelligence Agency's counter-terrorism center and sitting on the National Security Council's counter-terrorism subcommittee.

It's his mission, too, to ensure that the civil liberties of Americans, even those of groups whose ethnic or national backgrounds make them targets for suspicion during wartime, are preserved. Only recently, reminders of the bitter legacy of America's unjust internment of Japanese-American citizens during World War surfaced when Congress voted financial reparations for them and their families. And already Arab Americans are protesting that they are being unfairly singled out by FBI agents seeking information about possible terrorist activities.

These are daunting enough challenges for anyone, and Baker gives the impression of the type of cool, unflappable FBI agent who handles all pressures -- including months without days off, hours linked to secure phones, conferences with state and local police nationally, and security concerns expressed by other bureaucrats and officials -- with aplomb.

On a daily basis, Baker oversees the FBI's Strategic Information and Operations Center, which collects and assesses up-to-the-minute information about known terrorists and their infrastructure. Located on the fifth floor down a long corrider with white walls that make it seem more like a hospital than a center of high-level police investigative activitiy, the center was manned by a skeleton crew until August; now it is operated 24 hours a day.

Behind a heavy metal door marked "restricted access" in bold red letters, teams of workers sit before long lines of computers facing large TV screens while their supervisors observe them through enclosed glassed partitions and discuss new information and strategy around a conference table.

Last night's speech marked the second time in two days that Baker and the U.S. counter-terrorism effort confronted strains of what he euphemistically calls "Special Events Management."

The first was Sunday's Super Bowl game in Tampa. "The worst message that we could send to Saddam Hussein is that we curtailed a national treasure," Baker said, recalling conversations with "elected officials" about the Super Bowl that led to the decision to go ahead with the game.

Similar thinking dominated planning for the presidential address. To cancel it would send "the wrong message" to Saddam, as Baker put it, and hand him a psychological victory. Terrorism, he added, "is an attempt at victory on the cheap," and to disrupt such major national events would mean a victory for Saddam.

"Obviously when you get the entire leadership of the United States under one roof that has already been blown up rather successfully, there is tremendous concern," Baker said Monday afternoon when the long night still was ahead of him.

Despite the seriousness of the subject, Baker spoke with some humor, as shown by his wry reference to the bombing incident at the Capitol in 1983 and his description of the precautions taken for last night's speech.

"The Secret Service, the FBI, the Capitol Police and others have been working together toward this moment," he said. "We have a very well-trained hostage rescue team of 50 highly competent agents trained to deal with any exotic attack -- any that we can envision. And they are on immediate alert. The Secret Service and the Hill police will be there in abundance, and the sniffer dogs will have urinated on every chair by then. So I think they're making it a very secure place."

Taking such prevention action is only one side of the complex security equation. Threats to civil liberties are the other.

"We have a very important mission, but we must be able to do that mission within the constitutional guidelines and within our attorney general guidelines," said Baker, "and they're very explicit. So we do not follow an individual because of political statements made. . . . And that constitutional concern has to be protected even during a war."

As someone at the eye of this particular storm, Baker, 51, views his task with outward calm. His smooth, unlined face shows no hint of his daily stresses and his demeanor is self-effacing.

"What would be a victory for the terrorists is if we dramatically changed our way of life," he said, and cited his own family as an example of how that hasn't happened.

"My wife's a flight attendant, and she's still flying world-wide. We talked about it and decided: What else are you going to do? The point is, we have to take some precautions -- and we will."