The Battle of Baghdad may be a war game writ large - the trial by fire of a new American approach to combat.
It's a doctrine that calls for lightning strikes by ground forces, following relentless air assault and Special Forces operations against crucial targets.
In recent days, as US-led forces have struggled to maintain their stretched-out supply lines to the south, criticism of the US war plan has risen to symphonic intensity. The Pentagon wasn't prepared for attacks by irregular forces, say critics, and hasn't concentrated enough ground power at Baghdad's gates.
But top US commanders say they're confident that precision bombing has reduced the capability of the city's Republican Guard defenders by half, and that their plan is thus on track. The next few days, as US units probe Guard positions, might prove whether they're right.
"We'll be pushing the front lines ... to see if we can blow through there, so to speak," says Thomas Donnelly, a defense and security expert at the American Enterprise Institute in Washington.
At time of writing, it appeared that after pausing to restock and refuel, the lead elements of the US armored push into Iraq were turning their sights on Baghdad in an effort to regain the offensive.
Elements of the US 3rd Infantry Division clashed with the Republican Guard's Nebuchadnezzar Division on Monday in Hindiya, along Baghdad's outer defensive rim.
Meanwhile, fierce airstrikes hit Baghdad's southern and western areas. The US bombing campaign in the city appeared to be increasingly turning away from leadership sites and toward destruction of tanks, artillery, and other heavy weapons of the Nebuchadnezzar, Medina, Al Nida, and Hammurabi Republican Guard divisions.
"The air campaign has shifted focus dramatically in the past few days," says Michael Vickers, a military analyst at the Center for Strategic and Budgetary Assessments in Washington.
This doesn't mean that a major attack against Baghdad in the new few days, or even weeks, is foreordained. The US may be simply trying to pin the Republican Guard in place and continue to reduce its fighting power while waiting for the deployment of further US forces to the Iraqi theater of operations.
An advance group from the 2nd Armored Cavalry Regiment departed for Kuwait by air last Sunday from their base at Fort Polk, La. Much of the 4th Infantry Division has already arrived in Kuwait. Its shipborne equipment should be arriving shortly, and units of the division could move into Iraq within two weeks.
Tension between Secretary of Defense Donald Rumsfeld and the Army leadership has seemed to grow in recent weeks due to remarks by some in-theater commanders that they would have preferred more troops to start. Indeed, some experts now say that it looks as if US forces will delay any further major moves until more troops move in and the long supply line to Kuwait is pacified.
"They need more. It's obvious," says Barry Posen, a security studies professor at the Massachusetts Institute of Technology in Cambridge.
What's really needed, says Mr. Posen, is not so much the firepower of further forces as their manpower. Logistics, security, urban warfare - all suck up large numbers of infantry, he says.
The forces in Iraq now could still rout the Republican Guard and capture Baghdad if they had to, say other critics.
"We could defeat them with what we have, but it would take many more losses, much more time, and it would be exhausting for the soldiers," says Edward Atkeson, a retired Army general and land forces expert at the Center for Strategic and International Studies in Washington.
But more forces would be preferable, he says. In the first Gulf War, the US pushed Iraq out of Kuwait with 500,00 troops, as opposed to the less than half that number now back in the Gulf theater.
"The marginal cost of additional forces is not really important when you're looking at the enormous waste of a war," says Mr. Atkeson.
But to Secretary Rumsfeld that may represent an old way of thinking. He has long championed a military that is lighter, faster, more flexible, and more precise than the armor-heavy forces created during the cold war. And in this second Gulf War, he has been given the opportunity to at least test some of the doctrine that would underlie such a military transformation.
Thus the heavy reliance on airpower. Where only a small percentage of bombs dropped in the first Gulf War were precision-guided, virtually all munitions now used by the Air Force are steered by satellites or lasers.
Where the first Gulf War was more of a set piece, with weeks of bombing preceding the opening of the land campaign, the second has been marked by a "rolling start," in which the first troops to set foot on Iraqi soil actually moved before the bombing began in earnest.
Now may come the real test. Has US airpower destroyed Iraq's command-and-control, severing troops in the field from the Baghdad leadership? US officials say there are indications that is the case, as the Republican Guard units are not moving or fighting as if they are under unitary control.
Has the Republican Guard already been pounded into a fraction of its former self? US estimates hold that hundreds of tanks and artillery pieces and thousands of softer-skinned vehicles, such as trucks, have been destroyed in the southern Baghdad region - again, largely by US airpower.
The pessimism of critics is misplaced, say some analysts. "To me, the more appropriate analogy is to the first three weeks of the war in Afghanistan, when there was doom and gloom ... right before the whole northern half of the country fell, and a month before the rest of it fell," says Mr. Vickers.
The next few days may well show who is most right, the optimists or the pessimists, and whether the coming land campaign will continue for weeks, or months.
• Staff writers Linda Feldmann and Seth Stern contributed to this report.