While the operation in the urban battleground of Fallujah (search) has been called a major military success, U.S. troops are still evaluating the best way to destroy the enemy in city quarters while minimizing the impact on the civilian population that lives in those towns.

Some analysts say the best way is to let people know what's coming, even if it means warning the enemy of an impending offensive.

"Quite frankly, the best you can do is encourage people to get out of town when you know it’s going to be a battlefield and hope for the best," said retired Col. Gary Anderson, a military analyst with the Potomac Institute (search).

Civilian casualties are an inevitable part of the "collateral damage" inflicted when air strikes, artillery and mortar fire, direct fire and house-to-house combat are conducted in densely populated cities. And sometimes stories of overly aggressive U.S. conduct toward the enemy — such as the release of a videotape that shows a U.S. Marine shooting and killing a wounded Iraqi — raises questions about how the Americans treat civilians.

But, Anderson said, U.S. soldiers are concerned with limiting civilian casualties.

"An awful lot of thought has been put into it, but it’s a hard problem," said Anderson, who noted that a host of new technologies can better pinpoint targets, either from the sky or on the ground, and the military is always working on ways to do it better.

"But we aren’t yet to the point where we can truly minimize civilian casualties. We’re probably a long way away from that," he said.

Anderson and other military experts say that until technology is perfected, coalition forces are trying to reduce civilian deaths by engaging in more ground action using intelligence to single out the enemy, rather than striking solely by air.

"There is a downside in that there is a likelihood of a higher casualty rate among Marines," said Peter Khalil, a former advisor to the Coalition Provisional Authority (search) and now a visiting fellow at the Brookings Institution.

"But in the long term, I think it will save lives," he said, explaining that civilian deaths caused by Americans are used copiously to inflame the insurgency.

"If you use a precision-guided missile to take out a house with a few terrorists in it, you will get them but you might get civilians too, and then the brothers and the husbands and the fathers will join the insurgency as a result," Khalil said, adding that the Iraqi welcome mat is already wearing thin.

Meanwhile, much debate has been made over how many civilians have died as a direct result of the military operations since the United States invaded Iraq in March 2003. The Pentagon does not issue estimates so the Iraqi Ministry of Health (search) and independent organizations have been left to offer their assessments.

"We have no reliable means of gathering that information," said Pentagon spokesman Lt. Col. Barry Venable. He added that the military takes great care to avoid civilian casualties.

"U.S. military troops are disciplined professionals and we go to extraordinary lengths to limit civilian casualties and adhere to the law of war," he said.

Nonetheless, estimates of civilian casualties have ranged anywhere from 10,000 to 100,000. Most recently, in Fallujah, U.S. officials suggested the civilian casualty count was low because 80 percent of the population had already left before U.S. and Iraqi forces took over the city last week. The Associated Press reported on Sunday that civilian injuries from Fallujah are beginning to stream into Bagdhad hospitals.

Last April, IraqBodyCount.org, drawing off of news accounts and hospital records, estimated that 600 civilians were killed when the United States attempted to secure Fallujah after a spate of violent terrorist attacks there.

A study published this month in the Lancet medical journal and conducted in part by Johns Hopkins University scientists, concluded that 100,000 Iraqi civilians have died as a result of the war. Those numbers have been questioned because they are estimates based in part on a comparison of pre-war and post-war mortality rates and interviews with Iraqi residents, and do not distinguish between insurgents and civilians.

As of Nov. 8, the Brookings Institution Iraq Index has tallied between 3,520 and 5,025 deaths directly related to acts of war, either by coalition forces or insurgents, since May 2003. During that same period, it estimated between 16,800 to 31,400 deaths due to war plus the attendant violence from crime in a war-time environment.

A group of researchers behind IraqBodyCount.org say that based on extensive figures from the Iraqi Health Ministry and press and military briefings, they place the number of deaths due to direct war actions, suicide bombings, crime and health problems related to the war at 14,284 to 15,419 civilians since the U.S. invasion in 2003. In a separate study, the Health Ministry calculated almost 3,500 deaths from April 2003 to September 2004.

Experts say the Pentagon has not put out its own assessments because any talk about civilian casualties invites negative publicity.

"They don’t want you to know — that’s pretty straightforward," said retired Col. David Hunt, a FOX News military analyst. Hunt added that despite major "restrictions" placed on the soldiers to avoid civilian deaths, they cannot be avoided.

"It’s bad press," he said.

Anderson agreed. "I think it’s very dangerous to get into that number counting," he said.

John Sloboda, spokesman from IraqBodyCount.org, said that up until the official end of major combat in the war, marked as May 1, 2003, most deaths were caused by U.S. and coalition bombings. After that, there were many accidents due to unexploded ammunitions. Since then, he said, "It is much more mixed.

"It’s ground fire, being caught up in street battles, suicide bombs and simply the break down in law and order," he said.

"We are not in a sense trying to point fingers, but saying that things have become much more unstable and the instability is of interest to us," he said.

Sloboda said he thinks the true numbers are higher than their estimates because plenty of deaths go unreported or don’t turn up in local morgues or hospitals, from which the ministry gets its data.

The Lancet (search) report has drawn fire, but it has focused attention on the war’s collateral damage, he said. "I think what’s important is public awareness of what is going on," he said.

Khalil said the insurgency’s best weapon is twisting the Americans’ goal of liberation into a picture of murderous occupation. He said he doesn’t think it works overall, but warns that civilian casualties are mighty recruiting tools.

"It’s really important, among all of the media stories, to get across that the military is not coming in specifically to target civilians," he said. "It simply doesn’t happen that way."