Until now the new U.S. war in Iraq might have been termed "Rumsfeld's war," executed in a manner consistent with the defense secretary's vision of the future of the U.S. military -- heavily reliant on airpower, intelligence information, Special Operations troops and fast movement by regular ground forces, ideally all acting simultaneously to multiply their effect.

But whether it lasts days, weeks or months, the rest of the war promises to be fought like a slower, more methodical and traditional Army campaign that emphasizes the use of overwhelming force to defeat the enemy. Most notably, it probably will look more like the 1991 Persian Gulf War, which occurred when Secretary of State Colin L. Powell was chairman of the Joint Chiefs of Staff.

As they pause, regroup and reconsider their strategy, Army commanders in Iraq are reaching back to the conceptual approach used during that war under his tutelage. U.S. officers are less likely to roll the dice -- as with the "decapitation" cruise missile strike aimed at Iraqi President Saddam Hussein that opened the new war March 19 -- and more inclined to take time to amass their forces while airstrikes "prepare the battlefield" for their attack.

Under this approach, the two Army divisions engaged in Iraq probably will resupply and consolidate their positions for days or weeks before they attack the six Republican Guard divisions guarding the approaches to Baghdad. When that big battle comes, they will want to destroy the Republican Guard before moving on the capital, and that again is going to take time. Before entering Baghdad they also want to wait for the arrival of the tank-heavy 4th Infantry Division, which is moving to Kuwait from its base at Fort Hood, Tex.

It isn't surprising that Army commanders in Iraq are talking about such an approach. Of all the services, the Army has had the most strained relations with Defense Secretary Donald H. Rumsfeld. By contrast, said one general who served on a senior position on the staff of the Joint Chiefs of Staff, Powell has good relations with the Army despite having taken off his uniform a decade ago. Asked on Friday about the conduct of the new war by the U.S. generals in Iraq, Powell pointedly noted, "I trained them."

Army commanders say that they want to take the city of Najaf, astride their supply line, before beginning a major offensive against the Medina Division, the well-equipped Republican Guard unit that is dug in near the city of Karbala, about 50 miles southwest of the capital.

While they do that, they calculate, Air Force and Navy warplanes can bomb the Medina's tanks and other heavy weapons. Then Army artillery will pound fixed Iraqi positions and Apache attack helicopters will seek to destroy any tanks that try to reposition. Finally, tanks and mounted infantry troops will move in. This will replicate the sequence in the Gulf War, when under Powell's direction the U.S. military conducted five weeks of airstrikes on Iraqi forces in Kuwait before attacking on the ground -- and easily routing them.

But because much of the Medina Division is positioned among farming villages, the airstrikes can't be conducted with wholesale raids by B-52 heavy bombers, as happened during the Gulf War. Instead, tanks and antiaircraft guns will have to be hit one by one in what some pilots call "tank plinking" strikes. These take longer to erode enemy fighting power; they also have less effect on other essential military operations, such as a unit's communications and logistics operations.

"We are working over those Iraqi divisions with Apache helicopters," Air Force Gen. Richard B. Myers, the chairman of the Joint Chiefs of Staff, said yesterday on NBC's "Meet the Press." "They've lost a lot of their force. Their fighting capability is going down minute by minute, hour by hour." Yet some U.S. intelligence analysts closer to the battlefield think that so far those "retail" strikes haven't done much to reduce the combat effectiveness of the Republican Guard, mainly because it has received reinforcements.

All that stacks up to explain why some Army commanders think it could be a month or more before the battle for Baghdad is joined. There is no telling how long that fight will last. "Baghdad is not going to be easy," Rumsfeld said yesterday on "Fox News Sunday."

The wild card in all this is the Marine Corps, which is running its own operation further to the east in Iraq and is nearing the key town of Al Kut. To outsiders, the corps may look interchangeable with the Army, carrying the same weapons and driving the same tanks. But it fights in its own distinct way, tending to rely less on armor and more on infantry movements.

Some Army officers privately denigrate the Marines as low-tech, with more esprit de corps than modern equipment, and too willing to suffer casualties to achieve their mission. But the Marines are facing a Republican Guard division, the "Baghdad," that is lighter and has older equipment than that in the hands of the Medina Division that is facing the Army. That raises the possibility that Marines could break through their opponents before the Army does. Such an outcome probably would force an acceleration of the Army timetable.

Oddly, an expectedly rapid Marine advance through Iraqi lines would replicate another aspect of the Gulf War. Back then, the Marine attack into Kuwait was designed to be a "fixing" attack that tied down the Iraqi forces so the Army could smash into their western flank. Instead the Marines hit the Iraqis so hard that they precipitously withdrew from Kuwait before the Army attack could devastate them -- and so lived to fight another day.

The war still could end quickly with an unexpected collapse of Iraqi forces or the death of Hussein. "You never know when this thing is going to tip one way or another," Myers said yesterday on CNN's "Late Edition with Wolf Blitzer."

But if that surprise ending doesn't happen, the coming battles are likely to last weeks, even months, U.S. officers in Iraq now predict. If so, this spring will bring the longest spell of ground combat the Army and the Marines will have endured since the end of U.S. ground involvement in the Vietnam War 30 years ago.