RIYADH, SAUDI ARABIA, FEB. 1 -- The conduct of the first major ground battle of the Persian Gulf War remained clouded today well after it ended in an allied victory, as U.S. and Saudi military officials declined to discuss in detail what happened in and around Khafji this week.

Khafji, a sprawling Saudi oil town of 20,000 inhabitants on the gulf coast six miles south of Kuwait, was hardly a rich military target. But the ability of an Iraqi armored force to reach the town -- which U.S. and Saudi commands said was evacuated and undefended at the time -- and remain there for more than 24 hours, within easy reach of thousands of U.S. Marines and warplanes, has raised a welter of questions about how the war's initial ground combat played out.

Following are some questions raised by the attacks at Khafji and along the border farther west and the gaps left by answers from the U.S. and Saudi military commands:

How could an Iraqi tank battalion move early Wednesday into the Saudi town, even though it is a small one near the border, in the face of insurmountable U.S. air, sea and land power and Saudi Arabia's own nearby air and ground defenses?

U.S. commander, Gen. H. Norman Schwarzkopf and other U.S. officials have dismissed the Iraqi push as militarily insignificant, saying Khafji was undefended and so the Iraqis could just drive into town.

But the U.S. Central Command, in an official communique, announced that two Iraqi armored thrusts on Khafji in the pre-dawn hours Wednesday had been beaten back by "air assets." The command has not explained why, on the third Iraqi thrust toward midday, the aircraft did not defend the town as they had only hours earlier.

How were the Iraqis able to move on Khafji without being detected well in advance by U.S. satellites, reconnaissance planes, electronic monitoring equipment and U.S. and Saudi observation teams stationed along the border? How big was the attacking force?

A Central Command briefer, Brig. Gen. Pat Stevens IV, said Thursday that the Iraqi push into Khafji on the third try did not represent a failure in advance warning. "In fact, we probably have the finest ability to see the battlefield of any armed force in history," he declared. "So no, I would say there's no failure there, absolutely none."

Stevens declined to respond to questions why, in that case, the Iraqis were able to move what he initially reported as a light armored battalion, 400 to 500 men with their tanks, across the border and six miles down the highway without interference from the aircraft that, according to the command, had driven back the two earlier tank columns.

This question became more acute when Stevens a day later reported that Saudi forces, in retaking Khafji on Thursday and in subsequent engagements northward toward the border, captured more than 500 Iraqi prisoners.

"I don't know why we have so many prisoners of war," Stevens said.

For his part, the Saudi commanding general, Prince Khalid bin Sultan, told a news conference in Dhahran a few hours earlier that his forces captured 400 Iraqis. He said 30 Iraqis were killed and 33 wounded compared to 15 Saudis or Qataris killed and four wounded.

What was the U.S. role in the Khafji battle?

Stevens told reporters on Thursday that Marine Cobra gunships supported Saudi and Qatari forces trying to retake Khafji. But, echoing what Schwarzkopf had said on Wednesday, he added: "No Marine ground units were engaged in Khafji."

Pool reports from the city -- including television footage -- showed that in fact Marine artillery units were shelling Iraqi positions around Khafji. In addition, a Marine officer told pool reporters the tale of two Marine reconnaissance teams trapped inside Khafji who hid from the Iraqis and called in artillery and Cobra strikes during the fight.

Stevens today said he had used the word "engaged" in the strict military meaning of maneuvering ground troops. The Marine artillery fire, he explained, was only "support" and the reconnaissance teams got trapped in the fighting by accident.

How were Iraqi troops able to control the town for more than 24 hours?

Saudi forces, who had responsibility for the sector, had a Saudi marine garrison in Khafji earlier. But the unit was gone by the time the Iraqis attacked, leaving the city empty of Saudi troops when Iraqi tanks pulled in.

It has remained unclear whether the Saudi unit fled after the first Iraqi probes or pulled out under orders at an earlier point. More important, U.S. and Saudi officials have refused to describe what happened between the Iraqi entry about midday Wednesday and Saudi probes more than 12 hours later that culminated in a successful attack later Thursday morning that included house-to-house fighting.

A senior U.S. military source said privately that Saudi officers believed during the first hours of Khafji's occupation that they could induce the Iraqi force to surrender. At one point, the source added, the Iraqis appeared to be arguing among themselves about whether to give up.

How were 11 U.S. Marines killed and two wounded Tuesday night along the Saudi-Kuwaiti border south of Wafra, a town west of Khafji?

U.S. military officials have said only that the casualties are being investigated, including an effort to find out if they might have been killed by friendly fire from U.S. jets. Although 11 is a small number compared to the half-million U.S. servicemen in the region, these have drawn attention because they are the first U.S. killed-in-action from ground combat.

Schwarzkopf said Wednesday that the Marines were killed during a clash in which three U.S. light armored vehicles also were lost. This has led to assumptions that the soldiers burned when the vehicles went up in flames after being hit by Iraqi rocket-propelled grenades, anti-tank missiles or artillery fire. But these are only assumptions; the military has not yet said officially how the deaths occurred.

At the Pentagon today, spokesman Pete Williams said that "there's a very good possibility that we'll never know" who fired at the Marines.

"There are times when you simply can't tell the direction from which fire came. You don't know where the vehicle was when the fire initially hit it. Did it turn afterwards? Did it continue on for some period? . . . So I guess what I'm trying to say is we'll either know that it was friendly fire, enemy fire, or we won't know."