First hit would be Iraq's network of air defenses and communications. After that, Saddam Hussein's Republican Guard - in particular those troops closest to the border with Kuwait - and, if possible, production sites for chemical and biological weapons.

The overall strategy: Flatten as much as possible, as quickly as possible. And keep it up for days, maybe even weeks.That is a scenario emerging from discussions with senior military planners and defense specialists should President Clinton decide that diplomacy has had its day and it is time for a military strike.

"It's going to be a very different war; it's not a ground war this time," said Gen. John Sheehan, the retired four-star Marine Corps general who headed the U.S. Atlantic Command.

"The opening hours will be very violent," he predicted.

By next week, there will be nearly 10,000 ground troops in the region, but they would not see action unless Saddam threatens Kuwait. It was such an invasion that prompted the 1991 Persian Gulf War.

This would be far smaller than the gulf war - some 500,000 U.S. soldiers, sailors, airmen and Marines took part in Desert Storm, compared with 30,000 there now; 360 warplanes, compared with 1,000; and two aircraft carriers, compared with six.

But one advantage, says Sheehan, is the store of knowledge military planners have accumulated during years of monitoring and overflights of Saddam's forces.

"They know much more about how his system operates," said Sheehan, who was in charge of Marine amphibious units during the 1991 war.

Therefore, they know more clearly what they'd like to target.

"In as massive a way as you can, the objective would be to paralyze the system," said retired Gen. Merrill McPeak, who was Air Force chief of staff during the gulf war.

"The North Vietnamese would rebuild their (air defense) systems within days, and this guy's had years," Mc-Peak said. "I would never assume that this guy is a pushover."

Hundreds of Tomahawk cruise missiles would be launched at the air defense sites from nine Navy ships in the gulf. B-52s would unleash similar weapons, having flown closer to Iraqi airspace from bases on the Indian Ocean island of Diego Garcia. A key difference this time is that the missiles are no longer just guided by terrain but by satellite and can hit within a dozen feet from 1,000 miles away, and in any weather.

F-117 stealth fighter-bombers, lifting off from Kuwait, would use night cover to drop 2,000-pound laser-guided bombs at concrete command bunkers and communication outposts. Then, F-16CJ Fighting Falcons would smash what radars are left with high-speed, anti-radiation missiles.

That paves the way for the 100 strike jets that launch off the aircraft carriers USS George Washington and USS Independence in the gulf. Since the war, the Navy has outfitted its F-A-18 Hornets with laser-guided weapons, including the GBU-24s, which can be used to penetrate hardened targets. And the F-14 Tomcats, once only air-to-air fighters, now can drop precision munitions as well.

That means each aircraft carrier is loaded with three times the firepower one such warship had during the gulf war, Navy war planners say. Each carrier has practiced launching 200 bombing runs a day and can maintain that pace for four days in a row.

"This isn't going to be just a 25-Tomahawk launch. This will be a big deal and it will go for high priority targets from Day One," said a defense specialist knowledgeable about the planning. "You will degrade the system and keep it up until somebody yells uncle."

The official, who spoke on condition of anonymity, said "pause sequences" are built into the plan, primarily so that constant reassessments, and potential retargeting, can be done. "And after a pause, you go back and keep chewing it up."

While Iraq has about 382,500 active-duty soldiers, Saddam's premier troops are in his six Republican Guard divisions and four Special Republican Guard brigades. Those Special Guard units are thought to be the ones who protect Saddam's arsenals of suspected illegal weapons.

Speaking Tuesday at the Pentagon, President Clinton said U.N. inspectors believe "Iraq still has stockpiles of chemical and biological munitions, a small force of Scud-type missiles and the capacity to restart quickly its production program and build many, many more weapons."

Several "menu" options exist, so the military man in charge of the operation, Gen. Anthony Zinni, could call a halt within days, or keep the pace up for at least two weeks.

And plans exist to react should Saddam lash out, Zinni told reporters during his recent tour of the gulf.

"We've looked at every possible reaction to a strike, and we have sufficient branches and sequel plans to handle anything that might come up," Zinni said. Asked whether Saddam might respond with chemical or biological agents, the four-star Marine general said, "We look at everything, every possibility. We don't discount anything."

One crucial aspect for maintaining the action any length of time is the logistics and support network sustaining the operation, said retired Adm. Stan Arthur, who ran naval operations during the 1991 conflict.

"The support structure is key to the event," the Arthur said. High-flying spy planes, electronic jammers to disrupt Iraqi communications, Air Force AWACS and Navy E-2C Hawkeye command and control planes, numerous refueling tankers to keep bombing aircraft aloft, and search-and-rescue teams ready to pounce should a pilot go down - all must be tightly choreographed.