Chances of success for a NATO offensive in the last big Taliban bastion in Afghanistan's Helmand province may depend on ensuring the operation doesn't repeat the destruction of Fallujah in Iraq in 2004.

U.S. commanders have built up expectations the operation may help deliver stability to a deeply troubled country -- just as they did before fighter jets and tanks pulverized Fallujah in the name of protecting Iraqis from being terrorized by militants.

The plight of civilians may be the make-or-break issue for NATO, due in the next few days to launch one of the 8-year-old war's biggest offensives, to seize Marjah in Helmand.

Warning leaflets and the roar of U.S. fighter jets and artillery in the run up to Fallujah sent an unmistakable message to civilians to leave to avoid getting caught up in the siege.

This time, NATO forces have decided to advise civilians in Marjah not to leave their homes, although they say they do not know if the assault will lead to heavy fighting, raising the stakes.

The message to the people of the area is of course, keep your heads down, stay inside when the operation is going ahead, NATO civilian representative Mark Sedwill said this week.

Most of the population, estimated at up to 100,000, has stayed put, a possible vote of confidence in U.S.-led NATO troops.

Unlike previous Afghan military operations, the assault on Marjah has been widely flagged for months. Commanders say they hope this will persuade many fighters to lay down their arms or flee, reducing the eventual body count.

Civilians who have left the area, however, report insurgent fighters are digging in and preparing for battle.

MASSIVE RETALIATION

As Fallujah showed, it does not take many militants to provoke massive U.S. military retaliation. It was widely reported most of the most dangerous foreign al Qaeda fighters had fled before the battle and Iraqi militants stayed behind.

All it would take is a militant to stand on the roof of a house and fire on NATO troops to trigger the kind of firepower that demolished much of Fallujah, spreading anti-American sentiment and contempt for the U.S.-backed Iraqi government.

During one of many such incidents, a man with an AK-47 assault rifle was spotted on a roof. U.S. marines showed great concern and eventually fired a large anti-tank TOW missile at the building -- after mistakenly raiding the house next door.

The lack of the element of surprise may have given the Taliban plenty of time to booby-trap houses and cars in Marjah. That strategy paid off in Fallujah. House after house and many cars were rigged with bombs that slowed down the U.S. advance.

Aside from civilian casualties, the rows of crushed houses next to huge bomb craters all over Fallujah infuriated civilians who stayed and those who came back to find they had lost everything.

In Afghanistan, however, NATO commander General Stanley McChrystal's counter-insurgency strategy emphasizes seizing population centers and avoiding combat in built-up areas whenever possible.

He has strongly emphasized precautions to avoid killing civilians, and the number of civilians killed by NATO troops has declined since he took command in mid-2009.

It's not the number of people you kill; it's the number of people you convince. It's the number of people that don't get killed. It's the number of houses that are not destroyed, McChrystal has said.

That promise will come under closer scrutiny as the fate of civilians who stayed home becomes clear.

Human rights groups say that since NATO has encouraged people to stay, it bears an additional legal and moral responsibility to avoid heavy fighting that would cause civilian casualties.

The Taliban, like al Qaeda in Iraq, is highly unpredictable, increasing the chances meticulous planning and the best of intentions not to hurt civilians may not produce the desired results.

U.S. commanders in Fallujah often shook their heads after fierce battles.

As they drove intimidating, high-tech tanks through burning streets, militants would pop up out of nowhere, stand up and point their AK-47 assault rifles, knowing they stood no chance.

The same type of hardcore militants may challenge NATO troops in Marjah.

At the end of the day the Fallujah offensive achieved some objectives. The city was retaken and militants were killed. But it didn't really help stabilize Iraq. What followed was mass sectarian killings and the violence did not ease for years.

In Marjah time is of the essence. U.S. commanders will not have much leeway to reflect on the wisdom of their strategies.

The assault, the first since President Barack Obama ordered 30,000 extra troops to Afghanistan in December, is the start of a campaign to impose government control on rebel-held areas this year, before U.S. forces start to draw down in 2011.

(Editing by Bryson Hull and Jerry Norton)

Afghanistan Barack obama Al-Qaeda Iraq