The devastating air war that the United States launched last night against Iraq is the first part of a phased plan that American officials have drafted for the conflict.

The initial phase involved hundreds of U.S. planes, more than 150 Saudi planes and an unknown number of British aircraft. A senior U.S. official said the overall aim was to conduct "just over 1,000" bombing runs in the first 24 hours. The official count for the first seven hours was 750.

The course of the rest of the war -- whether long or short, bloody or relatively bloodless -- will depend in large measure on the success of U.S. air power in the coming days.

"There is some hope that Saddam will call it quits before the ground war begins," an Army official said this morning. He predicted the bombardment would last "days," adding, "Nobody in military circles really wants to pause. Saddam may not know how much damage he has taken, but we believe he anticipated taking heavy losses and we do not expect him to quit at this time."

Some of the targets -- Soviet-built surface-to-air missiles (SAMs), retaliatory weapons such as warplanes and missiles, command-and-control bunkers and communications antennas -- were long thought to be essential objectives of a successful opening salvo from the air.

Others, including main battle tanks and artillery, lay at the heart of Iraqi armored power, the key to its ability to resist a ground attack.

Still other targets, including munitions plants and chemical and nuclear facilities, were previously described by senior Pentagon officials as "strategic" and chosen to eliminate Iraq's long-term capacity to threaten offensive attack.

The intensity of last night's attack exceeded any since World War II. At the height of the Vietnam War's Christmas bombing of Hanoi and Haiphong in 1972, U.S. forces flew fewer than 1,400 sorties, or missions, over two weeks. At yesterday's pace, the assault on Iraq, which Defense Secretary Richard B. Cheney said was "likely to run for a long period of time," could exceed that number of sorties within a day.

In a statement at Riyadh, Saudi Arabia, fighter pilot Lt. Col. Mike Scott told reporters the assault force was made up of 12 kinds of aircraft, including F-4G Wild Weasel jets, A-10 Thunderbolts, F-117A "stealth" fighters, F/A-18 Hornets, AH-64 attack helicopters and B-52 bombers. Other officials said Tomahawk cruise missiles were launched from U.S. naval vessels in surrounding waters.

The stealth fighter incorporates "low-observable" technology designed to evade radar detection; the Tomahawk is a pilotless subsonic drone that skims so low it is hard for radar to track.

U.S. officials said the Tomahawks forced Iraqi defenders to turn on their radar, and that allowed the fighters to "home in" on the beams.

"We have not been targeting Mr. Saddam Hussein," Gen. Colin L. Powell, chairman of the Joint Chiefs of Staff, said last night's briefing. Instead, Scott said this morning, the targets included dug-in and fortified military installations; military air-defense radars, missile launchers and airplanes, and command and control targets such as the Iraqi Defense Ministry.

The initial phase appeared to have been highly successful, a defense official said, because there was no resistance from Iraqi warplanes and no launch of Iraqi

long-range Scud missiles, one of the most feared weapons in the Iraqi arsenal.

"The response from Iraq has been limited and U.S. air forces have experienced minimal resistance," Scott said. "The preliminary indications are encouraging."

A defense official said last night that 95 percent of the Tomahawks launched from naval vessels in the seas surrounding Saudi Arabia appear to have worked as designed, with the remainder aborting operation safely. He said the cruise missiles, along with the stealth fighters, were the first U.S. weapons to engage Iraqi targets.

Although planners weeks ago had anticipated a bombing campaign that would last a week or so before U.S.-led ground attacks begin, some Pentagon officials said earlier this week that the campaign could last a month.

Cheney said only that the results had been "very, very encouraging." Other officials suggested that the first night's assault had achieved not only pockets of local dominance, which planners call air superiority, but broader "air control" over the entire theater of operations.

U.S. commanders have described that control as central to their plans to defeat Iraqi ground forces. Some officials said last night that thousands of additional sorties would be flown -- against bridges, roads, supply dumps and other sources of strength and sustenance of Iraqi ground troops -- before U.S.-led infantry and armor would even need to consider entering the war.

The air war, Cheney said last night, is aimed at nothing less than the "destruction of Saddam's Hussein's offensive military capabilities."

Total allied air forces in the Persian Gulf exceed 2,000 planes, more than half of which belong to the U.S. Air Force. Those forces are expected to fly roughly 2,000 sorties a day against Iraq and drop as much as 5,000 tons of bombs daily. By comparison, the Rolling Thunder campaign in Vietnam involved about 3,150 attack sorties a week; the intense Linebacker II campaign in December 1972, credited with pushing North Vietnam to a peace agreement, dropped 20,000 tons in 11 days, according to historian Robert A. Pape Jr.

U.S. pilots hope -- and some are convinced -- that the relentless lash of allied bombing will so weaken Iraqi defenses and morale that the need for heavy ground fighting will be minimized. Lack of tree cover and a desultory Iraqi entrenchment effort -- fortifications are vast but some lack reinforced overhead protection -- make potential enemy targets extremely lucrative, pilots say.

The destructive power of modern air warfare is nearly unimaginable. One 2,000-pound bomb typically leaves a crater 36 feet deep and 50 feet in diameter; shrapnel from the blast is considered lethal in a radius of 1,200 feet. The payload from a three-plane "cell" of B-52s can crater an area 1 1/2 miles long and one mile wide. In Vietnam, even people hundreds of yards from the target area had their ear drums blown out by the concussion of the blasts. Dozens of B-52s are expected to be flying against Iraq.

But many Army and Marine ground commanders believe the air power enthusiasts are too optimistic, particularly if pilots fly most of their missions at mid-level altitudes -- three to four miles up -- to minimize losses from Iraqi small arms fire and antiaircraft guns.

"You can't count on accurately hitting dug-in tanks from 20,000 feet," one Army commander said recently. Iraq also has many hard-to-find mobile missiles and bomb-resistant aircraft shelters.

High on the war plan list were understood to be logistics targets such as rail lines, roads and fuel dumps to isolate occupied Kuwait from Iraq. Then come troop targets, including the elite Republican Guard divisions in southern Iraq and northern Kuwait. Some mixing of the sequence of these generic targets is likely.

Attack by ground forces is expected to follow, although perhaps not for several weeks. Pentagon officials have given conflicting assessments of whether President Bush is likely to impose brief pauses between bombing phases to allow Iraqi President Saddam Hussein -- or his successor, if Saddam is killed -- the opportunity to surrender.

The fact that the air war started at night signaled an important dimension of U.S. warring tactics: night fighting, long held in abeyance, is back in vogue.

In the 1970s, U.S. pilots practiced fighting at night by "kicking off some flares and then buzzing around like moths around a flame," as one senior F-15 pilot put it. Increasingly lethal surface-to-air missiles rendered the tactic too dangerous, and for much of the 1980s, Air Force pilots did not practice fighting in the dark. But new night-vision equipment and aircraft designed for night action -- like the stealth fighter -- brought night attacks back in vogue, just in time for the current war.

Though early reports last night spoke of little Iraqi resistance, American commanders have considered Iraqi air defenses formidable. In Vietnam, U.S. pilots basically faced one kind of SAM; Iraq has about 10, including sophisticated Soviet-made SA-6s, shoulder-fired SA-7s, French Rolands and U.S.-made Improved Hawks captured in Kuwait.

The best jets among Iraq's 700-plane air fleet are French F-1 Mirages, roughly comparable to Vietnam-vintage U.S. F-4s. U.S. pilots plan to "sort out" the enemy fighters at a 40-mile distance and fire air-to-air missiles at roughly 15 miles.

Of great concern to U.S. pilots are the hundreds of thousands of small arms and 4,000 antiaircraft guns possessed by Iraq. Most of the 2,500 U.S. planes lost in Vietnam were shot down by such weapons. The Iraqis appear to hold to the

Soviet "golden BB" doctrine: if enough bullets and other projectiles fill the sky during an air raid, at least a few are certain to find a vital target.

Consequently, instead of flying missions barely above the treetops, as U.S. pilots long planned to do against the vast SAM network of the Soviet Union, Air Force pilots hoped to destroy most Iraqi missile sites and fly the majority of attack missions out of range of small

arms.

Another major concern has been that allied pilots would unwittingly "mort themselves out," slang for shooting one another. "Fratricide is and probably always will be of very high concern to the commander because it certainly affects morale," said Maj. Gen. Billy G. McCoy, commander of Nellis Air Force base in Nevada.

To minimize such accidents, Navy, Air Force and allied pilots are likely to divide targets by time and sector -- Navy pilots striking an airfield north of Basra at 3 a.m., for example, while Air Force pilots strike a troop concentration south of Basra at 4 a.m. Even so, air commanders have acknowledged that fratricidal deaths will happen, especially in the "furball," as pilots call the confused tangle of air-to-air dogfighting.

Total U.S. losses in the air war are uncertain. The House Armed Services Committee estimated the number at 10 planes or more a day; Air Force officials believe losses will be lower.

Iraqi civilian losses also are inevitable and uncertain. The Rolling Thunder campaign killed an estimated 52,000 Vietnamese civilians between 1965 and 1968; Iraqi civilian losses should be much lower, U.S. pilots say, because U.S. experts have spent months planning ways to minimize "collateral damage." For example, military officials have plotted bomb runs so that munitions that fall short or long will miss hospitals, schools and the like. Senior defense officials have stressed recently that only military and military-industrial targets are at risk.

Many of the fighting principles and tactics that the Air Force is now using in the skies over Iraq and Kuwait were demonstrated this week over a remote range in Nevada.

The Air Force has conducted training missions near Las Vegas in recent days. A strike force of about 40 warplanes has swept north from Las Vegas after dark, rendezvoused for aerial refueling, then veered west across the Pahroc Range. While U.S. fighters engaged the Iraqi MiG-29 interceptors -- played by Canadian pilots flying CF-18s -- other American planes attacked a replica of military and industrial targets found near Basra, the large Iraqi city north of Kuwait.

By chance, the air space there is roughly the size of Kuwait and the distance from the runways at Nellis Air Force Base to the Range 75 targets is similar to the distance from the large air base at Dhahran, Saudi Arabia, to a prime target area near Basra. The 40-plane strike forces are similar to those being used against Iraq.

The Range 75 array illustrates Air Force thinking about targets. The range is filled with full-scale models of Scud and Frog surface-to-surface missiles, an airfield, SAM sites, a petroleum dump, oil derricks and other targets.

Staff writers Rick Atkinson, William Booth and researcher Lucy Shackelford contributed to this report.