WASHINGTON/KABUL (Reuters) - The frantic search for Bowe Bergdahl began the moment his comrades discovered he was no longer inside the fragile outpost in a rock-strewn valley in one of the most hostile corners of Afghanistan.

U.S. Army Sergeant Bowe Bergdahl waits in a pick-up truck before he is freed at the Afghan border, in this still image from video released June 4, 2014. REUTERS/Al-Emara via Reuters TV

Exactly why Bergdahl left is subject to intense scrutiny. But accounts by two Taliban sources as well as several U.S. officials and fellow soldiers raise doubt over media reports that he had sought to join the Taliban, and over suggestions that the deaths later that year of six soldiers in his battalion were related to the search for him.

His dramatic release on May 31 after five years in captivity in return for five Taliban commanders sparked a national controversy over whether President Barack Obama paid too high a price for his freedom. That was fueled by allegations by some in his battalion that he was a deserter, and that soldiers died because they were looking for him after his disappearance in the early hours of June 30, 2009.

While many questions remain, a Reuters reconstruction of his disappearance indicates that at the time when Bergdahl’s six comrades in the 1st Battalion of the 501st Parachute Infantry Regiment were killed in August and September 2009, his fallen comrades were on other missions like securing the Afghan elections and, according to one U.S. military official, the period of intensive ground searches had already ended.

But several soldiers in his unit say the quest to locate him never really ended, and that it was an element of every mission they undertook, prompting some to blame the deaths on him.

The U.S. Army has declined to give an account of those fraught weeks saying a new investigation will be conducted when Bergdahl, now being treated at a U.S. military hospital in Germany, is able to take part.

An initial investigation noted that Bergdahl had slipped away from his base in the past, once during training in California, only to return a short while later, according to people familiar with its classified findings. [ID:nL1N0OM1MW]

His disappearance in June 2009 came at a time of increasing attacks on U.S. forces from a resurgent Taliban: there were nearly 200 U.S. combat deaths in Afghanistan between the time of his disappearance and the end of 2009.

He had been on guard duty in one of the armored trucks parked in a circle on a dry riverbed to form a crude outpost in one of the most hostile corners of Afghanistan, in Paktika province along the border with Pakistan, according to several of his fellow soldiers.

They described him as a bookish loner who would rather learn Pashto than drink beer. Bergdahl, they said, had few close friends in the unit. “He definitely was very reserved, an introvert,” said former Sergeant Matt Vierkant, a team leader in Bergdahl’s platoon.

At roll call that morning, it became quickly apparent that he was missing - though his gun, ammunition and body armor had been left behind.

MISSING-PERSON REPORT

After searching the trucks, latrines, bunkers and quarters of Afghan National Police stationed with them, the platoon radioed in a missing-person report and immediately set out to search for him. Within two and a half hours, infantry units had fanned out to set up roadblocks and search nearby villages.

The area was tense. Three days earlier, Pakistani warplanes had launched a new offensive against the Taliban just across the border in South Waziristan, killing at least a dozen Taliban fighters in a rugged region known for heavily armed tribesmen and camps harboring al Qaeda and Taliban leaders.

As the search got under way, Vierkant, Bergdahl’s fellow platoon member, encountered two village children who said they had seen an American in Army clothes crawling through the weeds.

At about 2:30 p.m., a U.S. listening post picked up radio chatter indicating that an American soldier with a camera was looking for someone who could speak English, according to U.S. military records published by anti-secrecy group Wikileaks. Three hours later, they heard a U.S. soldier had been captured.

Taliban sources say they found Bergdahl walking alone after receiving a tip from local villagers.

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“Our people didn’t understand what he was saying at first because they don’t speak English. But later when they took him to a safe location, we realized that he wasn’t happy with his people and that’s why he left them,” a Taliban commander based in the Pakistani city of Quetta told Reuters on condition of anonymity.

The next night, Afghan National Police at the outpost where Bergdahl had disappeared received a radio call from the Taliban saying they wanted to trade 15 prisoners for the American, the military reports said.

Four days after that, the Army received a tantalizing tip - Bergdahl had been spotted in a black Toyota Corolla, flanked by men on motorcycles. He was wearing dark khaki clothing with a bag over his head.

That was the closest they would get for another five years.

Taliban fighters moved Bergdahl to Angoor Adda, a border town between South Waziristan in Pakistan and Afghanistan’s Paktika province. He was then taken to South Waziristan and later to the Shawal valley, a forested, mountainous area between North and South Waziristan, a Taliban commander based in Helmand province told Reuters.

Bergdahl did not show any interest in converting to Islam or joining the Taliban during those early weeks of his captivity, the commander said.

“We didn’t trust him as he could have been a spy. There were frequent drone strikes in the tribal areas and that’s why we were afraid of him,” he said.

Bergdahl has told U.S. authorities he was held in solitary confinement for long periods. The New York Times reported that he told medical officials in Germany he was kept in a metal cage in the dark for weeks after he tried to escape. [ID:nL2N0OP02F]

FRANTIC GROUND SEARCH

Bergdahl’s regiment searched for him at a frantic pace for several weeks. Where before troops might have had several days of down time to recharge between missions, now they would only return to their base for four to six hours - just enough time to gather more equipment and take a shower. Then it was back to the desert for another mission.

“When he walked off, everything changed throughout the whole province of Paktika. The mission for us and for everybody else was find Bergdahl as fast as you can,” Vierkant said.

Soldiers had to cope with temperatures that regularly climbed above 100 degrees Farenheit (38 C) and fine sand - known as “moon dust” - that worked its way into eyes, ears, and lungs, causing respiratory infections.

“It looked like I walked through a big bag of baby powder,” said former Specialist Billy Rentiers, who participated in the search as part of Easy Company, a support unit in the 501st regiment.

The increased number of missions at that time left troops vulnerable to attack more often, forcing them to step beyond the security of their outposts into hostile terrain, said several soldiers involved in the search.

Ambushes appeared to become more frequent and sophisticated during this time, the soldiers said.

In mid-July, military officials called off the dedicated ground search and gave soldiers other primary missions after concluding that Bergdahl had been taken to Pakistan, according to a U.S. military official speaking on condition of anonymity. The official said some Bergdahl-related surveillance continued for about another month, and soldiers were also told to keep an eye out and to ask about Bergdahl while carrying out primary missions.

CASUALTIES BEGAN

It was in mid-August that the battalion, still in Paktika province, started taking casualties. On Aug. 18, a roadside bomb killed Staff Sergeant Clayton Bowen, 29, and Private First Class Morris Walker, 23.

Bowen’s mother, Reesa Doebbler, says she was told by her son’s former comrades that he was on a mission to provide election security, an account confirmed by other sources, including a U.S. military official. Reuters was unable to contact Walker’s family.

Staff Sergeant Michael Murphrey, 25, died on Sept. 6 while setting up a security camp after a day spent distributing humanitarian aid, said Jack Kessna, a former member of Bergdahl’s Blackfoot Company who has worked with other former soldiers to determine the cause of the deaths. Kessna said Murphrey’s death could not be linked directly to the search.

Murphrey’s sister, Krisa, said she was never given official information about his mission after his death and had to rely on accounts by her brother’s comrades.

“Some say that he was not on a rescue mission, that he was on a humanitarian mission. And then some say that, sure it wasn’t a rescue mission, per se, but Bergdahl was always the secondary mission,” she told Reuters.

Staff Sergeant Kurt Curtiss, 27, was shot on Aug. 26 while his unit was supporting Afghan security forces during an enemy attack. Reuters was not able to contact Curtiss’ family.

On Sept. 4, Second Lieutenant Darryn Andrews, 34, died when enemy forces attacked his vehicle with a roadside bomb and a rocket-propelled grenade. Private First Class Matthew Martinek, 20, died a week later from wounds sustained in the same attack. The parents of both Andrews and Martinek told Reuters last week they believe their sons died searching for Bergdahl, saying they were told this by other soldiers in the platoon.

Former Private First Class Jose Baggett, who normally sat next to Andrews on every mission as driver and radio telephone operator, had been injured when a roadside bomb hit his truck on a previous mission. Martinek took his place.

“I even remember helping him pack his gear for the mission,” Baggett said. “Worst day of my life to date.”

Baggett says he doesn’t think the death of the two soldiers, or anybody else, can be directly linked to the search. Even if Bergdahl had not walked off, the battalion still could have taken casualties during its 12-month tour of Afghanistan, he says.

A U.S. military official said that, like the other casualties, the two men were not engaged in a search for Bergdahl but were on a logistics mission.

Vierkant believes otherwise.

“It was what every mission was, every day: find Bergdahl,” he said.