The big mystery about Operation Desert Storm for much of the first day was how well it seemed to go for the American and allied forces arrayed against Iraq.

All Wednesday night and well into yesterday, officials and outside analysts asked why Iraq had struck back so weakly at allied forces raining destruction from the air. Had Iraqi President Saddam Hussein simply been overwhelmed? Had he deliberately withheld his main response? Or were elements of both explanations at play?

By evening, however, Iraq had exploded any notion of an early rout by launching eight Scud missiles at targets in Israel and Saudi Arabia. While little significant damage was done, and officials continue to describe the Scuds as more of a political threat than a military danger, the late-breaking event suggested that any declarations about victory and defeat would be premature.

"Honestly, we don't know," said a Pentagon official, asked how well the military operation will go in coming days. Reflecting the mixture of enthusiasm and caution of some administration officials, he said: "In the next couple of days we're going to find out whether we're fighting pros or rookies here. I withhold judgment."

Other U.S. military officials did not conceal their exhilaration after the first 24 hours of fighting. Even with the missile launches, they said, the Iraqi response to allied air attacks has been modest.

Few Iraqi warplanes scrambled to engage the attacking allied forces, and U.S. accounts said antiaircraft fire shot down only four of the more than 1,330 U.S. and allied aircraft that bombed targets from Baghdad to southern Kuwait. Iraq's only other known success in hostile territory was an artillery salvo that set a spectacular blaze in three oil tanks at an inactive refinery near the northern Saudi border town of Khafji.

"We have silenced that" Iraqi artillery unit, said Gen. Colin L. Powell, chairman of the Joint Chiefs of Staff, in a metaphor that summarized the early fighting.

At the same time, however, officials such as Defense Secretary Richard B. Cheney cautioned that "everyone {should} be careful about claiming victory or making assumptions about the ultimate cost of this operation."

Powell warned of the Scud missile threat in a briefing early yesterday, noting that he was more confident American-led forces had knocked out fixed Scud launch sites than that they had knocked out mobile launchers, "a much more difficult target to find." A senior military official said later that several dozen of the mobile missiles "remain on the prowl."

Two primary theories about Iraqi strategy circulated among officials and analysts willing to discuss the question, although none had access to the most sensitive intelligence. One theory was that Saddam initially refrained from using his air force and long-range weapons in order to deploy them later to better advantage. The other said he had little choice about his initial weak response, having suffered catastrophically from the superior technology and numerical advantage in planes and weapons wielded by allied forces that had the advantage of surprise.

"There are three ways he can play his hand," said a senior official who favored the theory of voluntary restraint. "He could have preempted {the allied attack} with a strike against the Israelis or against us. He could put up everything he's got {in his air force} and fight. Or he can just try to ride it out" as part of a longer-term strategy to husband resources and drag out the war.

Some military officials and outside analysts said there was a simpler explanation.

"The fact of the matter is that a lot of folks have greatly overestimated the fighting capabilities of the Iraqi military," said John Mearscheimer, an expert on conventional warfare at the University of Chicago. "If they do come up into the sky, they'll be shot down very quickly."

A senior Pentagon official, cautioning against ebullience that marked some early discussions yesterday, said the skies over Kuwait and Iraq were "still a very hostile environment for our aircraft." Iraq's offensive arsenal, he said, has been "by no means eliminated. They still have an enormous military capability."

What engineers and military commanders describe as "unk-unks," or unknown unknowns, complicated the debate. Some questions were clear, officials said, even if their answers were not: How much of the Iraqi air force remained, and how many mobile launchers for the Scuds? But other questions, they said, might not even have been framed by planners, much less answered.

"We're going to be surprised by something, totally out of the blue," said a congressional official. "It happens in every war."

For a public bombarded with conflicting accounts and analyses, other uncertainties are at work. The rapid unfolding of events a great distance away -- in the context of operational secrecy and an open intent by U.S. officials to use deception against Iraq -- means that even professional observers are unsure what to believe.

Senate Armed Services Committee Chairman Sam Nunn (D-Ga.) said yesterday that some military threats are predictable. "There are considerable dangers," he said after attending a White House briefing on the war. He cited the threat of attacks by mobile Scud missiles, the risk of getting caught in a highly destructive ground war, and the possibility of terrorist assaults by Iraqi sympathizers.

A senior Pentagon official raised another possible concern. Asked why Iraqi air defense had not been more vigorous, he said Iraq could be holding warplanes in reserve.

But a congressional expert on Saddam's military said Iraqi pilots may have stayed on the ground out of fear.

"In the Iran-Iraq war, which is where we judge these things from," he said, Iraqi-flown MiG interceptor jets "turned around and ran away when they saw Iranian air defense fighters come their way." When Iraqi bombers faced air defenses in that eight-year war, he said, they usually fled and bombed irrelevant but undefended targets.

"This is not even a second-class air force," the expert said. "This is a miserable air force."

Other accounts credited superior U.S. electronic warfare capacity for the low losses of allied aircraft.

One flag officer said the Iraqi military apparently had no idea how much it was giving away by exercising its air defense radars until just a few weeks before Wednesday's attacks, nor how precisely ship-launched Tomahawk missiles could be programmed to find their targets if satellites overhead had time to map the land features in the surrounding area.

"I can't get over it," said one military planner. "It just seems that they were asleep over there and didn't think we'd bomb."

U.S. experts have been busy for months pinpointing the location and characteristics of each radar unit Iraq uses to detect incoming aircraft and guide its defensive missiles and gunfire, military officials say. With this knowledge, electronic warfare experts were able to tell allied pilots exactly how to destroy or blind the radar.

Air Force F-4G Wild Weasel attack jets, for example, knew the exact locations of radars guarding the most important Iraqi targets. The Wild Weasels first rushed these radar installations, provoking the Iraqis to turn them on. The jets then fired guided missiles into the Iraqi radar beams, specialists said, and the missiles rode the beams down to the sending antennas to blow them up.

Other Air Force, Navy and Marine planes also employed a combination of old and new techniques to incapacitate radar. By knowing the frequency and other characteristics of each radar facility, pilots were able to send back down to the ground exactly the same radar signal that was focused on their planes -- producing a blinding "snow" of static on the enemy gunner's radar screen.

Without such jamming, Iraqi gunners presumably would have seen the bright dots of attacking American planes on their consoles and could have targeted those dots for their antiaircraft missiles. Most Iraqi missiles are designed to ride up on the radar beams reflecting off the incoming aircraft.

When an Iraqi radar "paints" an incoming aircraft, a sensor light goes on in the cockpit. This warns the pilot to begin jamming and/or to take evasive action. The jamming can be done with old-fashioned chaff -- metal strips shaped to reflect radar signals -- or with equipment that duplicates enemy radar signals even if they are changed.

U.S. fighter-bombers were helped in their jamming effort by aircraft designed to generate blinding electronic signals, sources said. Jamming planes used in Wednesday's bombing raids, sources said, included the Navy's carrier-based EA-6Bs. The electronic warfare went beyond anything tried in combat before, sources said, and included tricks that made U.S. planes appear on Iraqi radar consoles to be at places far from their actual locations.

Staff writers George C. Wilson and Rick Atkinson contributed to this report.