Updated at 8:25 a.m. Eastern.
Minivans piled high with mattresses and clothing lined up at checkpoints as hundreds of civilians fled a Taliban-controlled area ahead of a planned NATO offensive in southern Afghanistan.
The militants, meanwhile, dug in for a fight, reinforcing their positions with rocket-propelled grenades and heavy weapons, according to witnesses.
The U.S. military has not given a start date for the operation to clear insurgents from the Helmand province town of Marjah, about 380 miles southwest of Kabul.
American troops are ready, however, taking up positions surrounding the town and well aware of the dangers that await. CBS News correspondent Mandy Clark, embedded with U.S. Marines about five miles from Marjah, reports that the American Special Forces are already entering the town at night in advance of the operation.
The biggest fear, and one which is well founded based on what Taliban sources tell CBS News, is improvised explosive devices, or IEDs - the militant's weapon of choice.
U.S. commanders tell Clark they will enter Marjah using a staged approach to try and minimize casualties from the IEDs, which they believe the area to be "seeded" with.
"Assault Breacher Vehicles" - hulking tank-like, blast resistant machines with digging equipment on the front, will be first to enter Marjah, trying to clear as many IEDs as possible. They'll be followed by progressively larger groups of troops.
CBS News producer Ben Plesser reports that Marjah is the last town in the restive Helmand River Valley - once firm Taliban territory - to remain under control of the militants in the wake of a massive coalition offensive in December.
The military has said fighting will start soon, though no exact date has been given, and many residents weren't taking any chances.
In addition to the bombs planted across the town, commanders tell Clark they expect to encounter between 400 and 1,000 Taliban fighters in Marjah.
American aircraft dropped leaflets over Marjah on Sunday warning people of the coming offensive, officers said, and the U.S. fired illumination rounds after sundown, apparently to help spot Taliban positions.
Villagers said the leaflets were aimed primarily at the militants, listing several of their commanders by name and warning fighters to leave the area or be killed.
Since being pushed out of surrounding areas by U.S. Marines, Taliban forces have had months to bury roadside bombs in anticipation of the assault, reports Plesser. Increasing the difficulty, the land is broken up by irrigation canals, built by the U.S. in the 1950s and 1960s, that could stop the advance of tanks and other assault vehicles and shelter militant snipers.
U.S. Gen. Stanley McChrystal, the top NATO commander in Afghanistan, said the success of the operation depends on convincing civilians that the government will improve services once the militants are gone.
The offensive in Marjah - a farming community and major opium-production centre with a population of 80,000 - will be the first since President Obama announced he was sending 30,000 additional troops.
Afghan President Hamid Karzai discussed the on-going operations in Helmand province in a telephone conversation Sunday with British Prime Minister Gordon Brown, a spokesperson for Brown said.
The spokesperson said they "welcomed the leading role" played by Afghan Security Forces in preparing for the offensive, stressing that "Afghan leadership was fundamental to the success of the operation."
U.S. officials have long telegraphed their intention to seize Marjah. McChrystal said the element of surprise was not as important as letting citizens know that an Afghan government will be there to replace Taliban overlords and drug traffickers.
"We're trying to create a situation where we communicate to them that when the government re-establishes security, they'll have choices," McChrystal told reporters Sunday.
British Defense Secretary Bob Ainsworth told reporters over the weekend that the leafleting and long advance warning of the operation in Marjah were meant to warn militants to either leave the area or lay down their arms, as the military's goal was not "slaughter".
The International Committee of the Red Cross said there was no way to count the number of people who have left Marjah because many have moved in with relatives or rented houses in nearby towns instead of registering for emergency relief.
ICRC spokesman Bijan Farnoudi noted a first aid post in Marjah had recorded an increase in patients with battle wounds in the last few weeks.
He said the organization was poised to react quickly if a refugee crisis arises. "The burden on families taking in relatives for an extended amount of time can be significant," he said.
Ghulam Farooq Noorzai, the head of the provincial refugee department, estimated that 90 to 100 families had left the Marjah area because of concerns about the operation. Afghan families have an average of six members, according to private relief groups.
Refugee officials held an emergency meeting last week and decided to stockpile food and erect five big tents on a school compound in the nearby provincial capital Lashkar Gah to accommodate any influx, he said.
Mohammad Hakim, a 55-year-old tribal leader in Marjah, said fear has risen over the past two weeks and he knows at least 20 families who had left. He himself planned to take his wife, nine sons, four daughters and grandchildren to live with relatives in Lashkar Gah.
"Everybody is worried that they'll get caught in the middle when this operation starts," he said in a telephone interview.
Hakim said he was worried about the length of the operation.
"I can stay for one or two weeks," he said. "But if I have to leave my agriculture land for months and months, then how will I feed my family?"
Afghan and NATO officers had visited village elders to encourage them to make sure people stay inside their homes and avoid road travel once the operation starts.
The Taliban were not preventing villagers from leaving but were digging trenches and carrying in new heavy weapons on motorbikes.
Many people were afraid to leave their fields and brave the bad winter roads, villagers said.
Ghulan Nabi, a wheat and poppy farmer with seven children in Marjah, said his family planned to leave soon and wait out the offensive in a nearby district.
"We have a good house, a nice life, but now I will have to rent a home," he said. "But we want peace and security. We don't care who comes here. We just want peace in our village."