Washington (CNN) Sgt. Bowe Bergdahl told the military he left his unit in eastern Afghanistan in July 2009 intending to walk to the nearest U.S. military outpost to report wrongdoing, believing he could not trust his own commanders to deal with his concerns, according to sources familiar with the Army investigation. It is the clearest indication yet of the motive behind his decision to leave his post.

Bergdahl was planning to report what he believed to be problems with "order and discipline" in his unit, a senior Defense official tells CNN. A second official says Bergdahl had "concerns about leadership issues at his base."

This information is part of the report presented to General Mark Milley who this week decided to charge Bergdahl with desertion and misbehavior before the enemy. This information outlines what could be a key part of Bergdahl's defense, which the army is already aware of.

Both officials declined to be identified because of the legal proceedings against Berghahl, but both have direct knowledge of the information outlined in the report. "This was a kid who had leadership concerns on his mind," the second official said. "He wasn't fed up, he wasn't planning to desert."

What Bergdahl's concerns were, and whether they are relevant to the case of desertion the Army is trying to make will be a matter for military authorities to decide. "I can't tell you if his concerns were valid, but in his mind they were," the official said.

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