TIME has a good overview of what a second Gulf War might look like.

The second Gulf War, if it comes, would be more like the Big Bang—hundreds of towering explosions all across Iraq all at the same time. The Pentagon buzz word for this is simultaneity. The plan would have unprecedented numbers of smart, satellite-guided bombs attack a multitude of targets over a great sweep of territory, swiftly followed by U.S. troops seizing key objectives.

More:

The Iraqi military would stand largely defenseless before this onslaught. U.S. tanks could destroy Iraqi tanks before the Iraqi tanks could even detect the American armor. B-2 bombers fly beyond the reach of Iraqi guns, and invading U.S. troops should be able to drive around flaming, oil-filled ditches or other defensive measures; U.S. troops call them speed bumps. If the Iraqis elect to stand and fight, the Pentagon fears, they would unleash hidden stores of chemical and biological weapons on advancing U.S. troops.

And they should be afraid of this. I'm not sure the Iraqi soldiers have to "stand and fight" for CBW to be used, and the threat isn't only that it would be used against U.S. troops, but against Iraqi civilians. This could be a very ugly war, but it sounds like the military planners are fairly grounded in reality about the prospects.

Civilian casualties are a political and military nightmare. Human-rights groups estimate that about 3,500 Iraqi civilians died in the 1991 war. U.S. officials refuse to estimate the numbers of civilian expected deaths in a second Gulf War. It could get extremely messy, with the carnage broadcast instantly around the world. "What appears on al-Jazeera TV in the region is going to determine success maybe even more so than the actions on the ground," says retired Marine General Anthony Zinni, who ran Central Command from 1997 to 2000. "All the explanations afterwards won't counter those first images."

And on a similar note:

"War is inherently violent. People are going to die," Myers said last week. Americans should not look to the relatively antiseptic wars for Kuwait and Kosovo as a guide. If it were to come down to fighting block by block in Baghdad, the images could be brutal. "We have to be mentally prepared for that," Myers said.

Yes, we should. And I fear many people, especially some of those who support military action, aren't. But we need to be.

The people planning this war seem to be much more realistic than those arguing about whether or not it should happen. From near the end of the article:

Franks said last week that the answer to the most important questions about the war—how long it might last and how many might die—are "unknowable."

Of course they are. A war is a complex, chaotic phenomenon. The outcome is impossible to predict. There could be hundreds of thousands of civilian casualites, especially if Hussein decides that if he's going down, he's going to take as many people as possible with him.

This war could be extremely brutal and ugly. The primary question that needs to be honestly answered is: Would more death and suffering occur further down the road if we didn't take action now?

As I've stated before, I don't unequivocally know the answer to that question. I believe the answer is yes, because I think Saddam will never stop trying to acquire nukes, and he will continue to stockpile biological and chemical weapons, and that eventually they would be used, primarily as an umbrella for renewed aggression against his neighbors. I think he will have to be confronted sooner or later. His ambitions will not wane. And I believe the risks are less if we act now, rather than face him at some distant point in the future when he has even more, and even worse, weapons.