Iraqi forces surprised U.S. military officials this week by demonstrating new skills even though they were badly defeated in their first ground combat with the coalition forces arrayed against them, several officials said yesterday.

The Iraqi moves into Saudi Arabia late Tuesday and early Wednesday suggested extensive preparation and a high degree of coordination through a line of command U.S. officials suspect stretched all the way back to Iraqi President Saddam Hussein, the officials said.

Leaders of the four attacking Iraqi battalions also displayed an important ability to move armored and mechanized columns through deployments of front-line Iraqi troops at night, tactics rarely observed either during previous Iraqi maneuvers or its eight-year war with Iran.

Officials said the operation was risky because between 1,500 and 2,000 Iraqi soldiers had to thread their way during darkness through thousands of mines and other fortifications deployed by the Iraqis in southern Kuwait while avoiding potential "friendly fire" from thousands of other Iraqi soldiers.

Early reports reaching Washington indicate that the Iraqi incursions were eased by night-vision and infrared equipment of a type that attracted immediate notice among U.S. intelligence experts. No details of the equipment, apparently obtained from foreign suppliers, were available yesterday.

But once inside Saudi territory, the Iraqi forces suffered a withering and highly effective assault. During a retreat, some became entangled in their own minefields and border fortifications and were picked off by U.S. A-10 and Harrier aircraft and by Cobra helicopters, the officials said. A series of other skirmishes left several dozen Iraqi tanks and armored vehicles in ruins. Up to 500 Iraqi soldiers were captured, officials said.

Saudi Gen. Khalid bin Sultan -- the commander of Arab forces that ousted Iraqi forces in a house-to-house battle in the deserted, seaside city of Khafji -- yesterday said the Iraqi attacks had "all the characteristics of a suicide mission." But a U.S. Army official said the operation "was well-planned, even sophisticated in part, but poorly executed."

The preliminary tally when combat ceased Thursday was at least 30 Iraqis dead, plus 11 U.S. Marines and 15 Saudi soldiers. The invasion force was driven back across the border, with no enduring gains on either side. One U.S. military official described it as a "militarily insignificant engagement that should not be seen as an accurate vignette of a broader ground war."

At least three possible explanations have been offered for the Iraqi assaults.

One suggests that by moving south and then retreating at different points along a 45-mile stretch of the border, the Iraqis were able to gain valuable intelligence on the positions and capabilities of U.S. and allied forces. Because the United States completely controls the airspace over southern Kuwait, "they really don't have any idea where we are," a U.S. official said.

A second possible reason was Iraqi frustration over the repeated shelling of their forces by U.S. Marines south of the Saudi-Kuwaiti border in the past week, which the Iraqi attack was able to disrupt. A third reason may have been Iraqi desire to "inject a dose of morale into troops that have been pretty well mauled by the enemy" by signaling that it could still take the offensive, one official said.

British military intelligence sources said some Iraqi forces fought fiercely in the raid, belying accounts by defectors who earlier claimed that troops in Kuwait suffered from hunger and low morale. "How they fought at Khafji is more important than the anecdotal evidence we received" from defectors, one official said.

U.S. officials have said they believe communications links between Iraqi forces in Kuwait and Baghdad have been damaged but not destroyed in the past two weeks of aerial bombardment. A source who has been briefed on the attack said "no one believes there has been so much damage to Iraqi command and control capabilities that these were independent events."

Each of the four Iraqi battalions involved in the assaults was moved south, along with other division-sized Iraqi forces, and then threaded through front-line troops and minefields in a narrow column of single vehicles, U.S. officials said. "This is a capability we have not seen them execute before," one official said. "It's like groping around in the dark with lots of dangers around."

U.S. officials have long credited the Iraqis with only limited capability to operate at night, by using infrared sensors and special telescopes that collect and amplify reflected starlight. "We have always said the darker the better," a U.S. official said, in the belief that U.S. and allied night-vision equipment is far superior, putting Iraqi forces at a substantial disadvantage.

One official said the limitations of Iraqi training were evident when one of the Iraqi battalions operating roughly 15 miles west of the Kuwaiti oil fields at Wafra retreated under fire from U.S. Marines. "They failed to find the opening in their own fortifications, ran into some mines, and got eaten up" by attacking aircraft, he said.

Although the Iraqi mechanized and armored units brought some artillery into Saudi Arabia, they evidently never had an opportunity to use it. Without aircraft or surface-to-air missiles, they also lacked protection against devastating attacks during more than 300 sorties by U.S. and allied aircraft on Wednesday and Thursday.

A Saudi official said yesterday that enough Iraqi equipment had been captured to outfit two battalions. A Marine official said 22 Soviet-made T-62 tanks were destroyed by U.S. TOW missiles, and many other Iraqi armored vehicles were destroyed by aircraft.

Correspondent Glenn Frankel in London contributed to this report.