Two gripping images from the war this week: Army Rangers under fire, creeping onto a bridge to rescue an elderly Iraqi woman who had been wounded in the crossfire. A Toyota van filled with women and children failing to stop at a US Army roadblock and now riddled with deadly cannon fire.
This war, like all wars, presents the profound dilemma of force protection versus collateral damage - the shifting and sometimes deadly relationship between keeping ground troops from harm and the moral and political imperative to avoid death and injuries to innocent civilians.
Every day in Iraq, young US troops and their officers - most of whom are in combat for the first time - have to make such snap decisions. In some cases, they kill or capture Iraqi fighters dressed in civilian clothes. In others, like the van incident in which up to ten of 11 women and children were killed at a checkpoint, their instinct for preservation turns tragic.
For many military experts, such scenes raise the specter of other difficult situations involving soldiers and civilians: Northern Ireland, Lebanon, Israel and the Palestinians. In those cases, years of what many considered to be an occupation dangerous to soldiers and civilians alike delayed or prevented ultimate peace.
"The conundrum is, How do you win the war and still win the peace?" says Charles Peña of the Cato Institute in Washington. "Every civilian casualty is a little bit of evidence that we're killing the people we're supposed to be liberating."
In response to the recent suicide bombing that killed four American soldiers, as well as many instances of enemy fighters found in civilian clothing, the Pentagon has tightened its rules of engagement in Iraq. All drivers and passengers at military checkpoints will be searched. Those who approach such posts on foot and refuse to comply with verbal orders are more likely to be shot.
"The inherent right of self-defense is the starting point for any of our rules of engagement," Brig. Gen. Vincent Brooks said Tuesday at Central Command's daily briefing in Qatar.
As for the civilian deaths at the checkpoint, General Brooks said, "The blood is on the hands of the regime."
Hiding among civilians may violate the laws of war, but it's one of the most effective tactics a weak defender can adopt, says Loren Thompson of the Lexington Institute.
"It maximizes the likelihood of successful engagements, minimizes the invader's ability to help or convert civilians, and saps the attacker's will."
Which brings to mind Mao Zedong's famous dictum on the subject: "The guerrilla must move among the people as a fish swims in the sea."
That may have worked for the Chinese Revolution, and it may be something that Saddam Hussein's paramilitary fighters have taken to heart. But it's also extremely dangerous for civilians just trying to stay out of the battle - including those in and around Baghdad whose neighborhoods include military installations purposely placed there.
American officials do not want to repeat such earlier mistakes as the bombing of a Baghdad air-raid shelter during the first Gulf War that killed upwards of 400 people, the destruction of the Chinese Embassy and a passenger train in Belgrade, and the attack on a wedding party and Red Cross facilities in Afghanistan.
Up to now, the United States has lost some 50 service members in Iraq. Civilian casualties are estimated to total about 500. At the Central Command briefing Tuesday, Brooks was pointedly asked if the US would be willing to accept a 10-to-1 civilian-to-military casualty ratio in the coming battle for Baghdad.
"We'd like to see it be zero," he replied, but given the uncertainties or war - especially the amount of firepower involved - there was no way he could have been more specific than that.
Michael O'Hanlon, a military analyst at the Brookings Institution, notes that incidents like the attack on the civilian van are regrettable but small in scale. "Errant bombings are still the big worry, plus urban combat," he says.
Urban combat, albeit on a lesser scale than what could occur in Baghdad, already is occurring in Iraq's southern cities - some of it door-to-door with fixed bayonets. Although American troops have had some training in this kind of fighting, some experts say it hasn't been enough.
"Even [new] rules of engagement won't solve the problem," says Mr. Peña. "For starters, our troops are trained largely to fight conventional wars against a conventional enemy. Iraq is anything but. Also, we're foreigners in a foreign land. That means we don't speak the language. So how exactly are we supposed to communicate to the people what they're supposed to do?"
For some, this means accepting a certain level of civilian casualties - as terrible as that is - in the name of a military victory that defeats a repressive regime and may save more lives in the long run.
"But, of course, if too many civilians are killed, it makes the Iraqis fight harder, will probably lead to the influx of foreign fighters from other Islamic nations, and will make the civilian population even more hostile for any US postwar occupation," says Ivan Eland of the Independent Institute in Oakland, Calif.
"Winning hearts and minds is paramount in any guerrilla war - and especially when the people dislike the United States to begin with, even the Shiites," says Mr. Eland. "But, of course, that contradicts force protection when guerrillas are intermingled with the populations. Hence the dilemma."