Last March, Mrs. Bales wrote on her blog that her husband had not gotten the hoped-for promotion to sergeant first class, which would have raised his pay by about $370 a month and made him eligible to be the senior noncommissioned officer for a platoon. (He was also paid an extra $400 a month during his deployments.) The promotion probably would have also given him some peace of mind about his Army career, which was nearly halfway to the 20 years needed for retirement with pay.

Though “sad and disappointed” by the news, Mrs. Bales said she was also relieved. “We can finally move on to the next phase of our lives,” she wrote.

The Final Deployment

That next phase, the Baleses hoped, would take them to Germany, Italy or Hawaii. But the Army did not move Sergeant Bales from Joint Base Lewis-McChord. Nor did it allow him to become a recruiter, though he was in training for the job. Instead, he was told he would go with the Third Brigade to Afghanistan in December.

“He was not happy about it,” Mr. Browne said, but took his orders like a professional soldier.

Before deploying, Sergeant Bales would have undergone physical exams, including on his foot, and a computer-based survey for traumatic brain injury intended to measure attention, memory and thinking ability. The survey is not well regarded among many specialists, but it remains the Army’s chief screening tool for traumatic brain injury. Sergeant Bales was declared fit to deploy.

Little is known about his time in Afghanistan, other than that he and others in his battalion were assigned to work alongside Army Special Forces soldiers in the Panjwai district of Kandahar Province, a longtime hotbed of Taliban activity that has grown more secure in recent years. Sergeant Bales would probably have provided security for the Green Berets while they carried out night raids, built relations with village leaders and organized local militias.

A Green Beret who has spent time in Panjwai in the past year said the combat outpost would have been relatively small, protected by dirt-filled containers known as Hesco barriers, with guard towers and perhaps a blimp with a high-powered camera capable of capturing images more than a mile away. It would have been difficult, but not impossible, for Sergeant Bales to slip away at night unnoticed, as the Army says he did.

Supervision in the outpost might also have been more lax than at larger bases, which could explain the presence of alcohol. Sergeant Bales might have even been among the more senior noncommissioned officers on his team. Special Forces teams typically have 12 members, sometimes fewer, and Sergeant Bales’s unit might have been as small as a platoon of two dozen soldiers.