When a mortar shell killed three people at his neighbor's house, Munir Khan knew it was time for him and his family to pack up and leave his village near the Afghan border.
In doing so, they joined around 1 million other people still displaced as a result of fighting between Islamist militants and Pakistan's army.
The displaced have become the forgotten victims of Pakistan's U.S.-backed campaign against militants, living in camps or relatives' homes scattered throughout the country. That so many have still not returned is perhaps the clearest sign of the difficulties the army is facing against deeply entrenched insurgents along the frontier.
The White House this month issued a report that said continued military operations in the Mohmand region _ an area about the size of metropolitan Paris and all its suburbs _ illustrated Pakistan's inability to keep its tribal areas free of insurgents.
The report noted that there have been three such pushes in the remote, lawless region in the last two years. The Pakistan government has rejected the report's conclusions.
In some northwestern regions, the army has declared victory _ only to see militants return and residents flee for a second time.
Khan fled his home April 5 after fresh clashes between the army and militants very close to the border began around the same time. The government says 142 militants have been killed in air and ground attacks, but there is no way to verify that figure and it could well be inflated or include civilians.
He and his family walked for two hours before taking a car to the main northwestern city of Peshawar.
"I thought we could be killed ... so better to take the risk" of traveling through a war zone, said Khan, a thin, 34-year-old who buys and sells marble from quarries in the region _ one of the main industries in the area.
He did not know who fired the mortar shell, but security forces and insurgents both use such weapons.
Al-Qaida and Taliban fighters fled from Afghanistan to tribally administered regions like Mohmand soon after the 2001 U.S.-led invasion there. They have since been joined by Pakistani militants who are waging a war against the country's secular leaders. Also joining them are international jihadists seeking a sanctuary and training ground.
The U.S. wants Pakistan to succeed because the tribal areas are also being used as staging areas by militants fighting Western troops across the border in Afghanistan. Many of the suicide bombers used in Afghanistan are young boys from Pakistan's side of the border, the U.N. has said.
The White House report said at least 6,000 Pakistani security forces were dispatched with air support at the start of 2011 to rid Mohmand of militant groups, but they have struggled.
In Iraq and Afghanistan, the U.S. military strategy has been to "clear, hold and build" _ eliminate insurgents from a given area, ensure there are enough troops on the ground to stop them from returning, and then build roads, schools and other development projects to try to win the support of the people.
"What remains vexing is the lack of any indication of 'hold' and 'build' planning or staging efforts to complement ongoing clearing operations," the report said.
This month, some 5,000 families _ roughly 40,000 people _ have fled their homes in Mohmand, said Amjad Ali Khan, the region's top administrator. The United Nations said 500 families had arrived in the Nahqi relief camp in Mohmand, but that others may be staying elsewhere.
Army operations against militants since 2008 have caused waves of people to leave their homes in the northwest.
Many have returned, but around 1 million people remain in camps or with relatives and friends, the U.N. says.
Pakistan's military, trained to fight conventional warfare against Indian troops on the plains of the Punjab, have had trouble adopting counterinsurgency tactics in mountainous areas. The force has relied heavily on air attacks, which risk civilian casualties.
It says it has lost more than 3,000 soldiers since 2001 fighting the militants and has launched operations in six of the seven tribal areas, the largest being in South Waziristan region.
There, about 30,000 ground troops launched an offensive in October 2009, quickly clearing what had been a major hub for al-Qaida and the Taliban. But 400,000 people fled the region _ most of its population _ and more than 90 percent have yet to return.
"Presently, the security situation in South Waziristan is not satisfactory and we cannot tell our people to go back," said tribal elder Maulana Asamuddin.
One way Pakistan's military has tried to stem the militant tide has been by enlisting local tribes to set up their own fighting forces, known locally as "lashkars" or "peace committees." That strategy has run into difficulty in Mohmand, with many tribesmen reluctant to join.
"We were in trouble from both sides," said Khan said. "The elders of those tribes reluctant to join peace committees were being arrested and tribes were being punished. And those joining the committees were becoming targets of the militants."
Because of a curfew and ongoing militancy, the marble industry had shut down in the past year because workers did not come to the quarries, and there was little commerce or agriculture, he said. The only school in Khan's village of Ghanam Shah was destroyed by the insurgents.
Now, Khan and his family are staying with relatives, and hoping for a quick end to the fighting.
"I don't want to go to government relief camps," he said. "There, life will be more difficult, I think, than in our village."
Associated Press writers Nahal Toosi in Islamabad and Ishtiaq Mahsud in Dera Ismail Khan contributed to this report.
(This version CORRECTS that 1 million people are still displaced, not have fled, and that the South Waziristan offensive was launched in October 2009, not September.)