After almost three years in custody, the soldier accused in the biggest leak of classified material in US history said he did it because he wanted the public to know how the American military was fighting wars in Iraq and Afghanistan with little regard for human life.
Manning, 25, pleaded guilty Thursday at a military hearing to 10 charges that could carry a maximum sentence of 20 years. Prosecutors plan to pursue 12 more charges against him at court-martial, including a charge of aiding the enemy that carries a potential life sentence.
"I began to become depressed at the situation we found ourselves mired in year after year. In attempting counterinsurgency operations, we became obsessed with capturing and killing human targets on lists," the former intelligence analyst in Baghdad told a judge.
He added, "I wanted the public to know that not everyone living in Iraq were targets to be neutralised."
It was the first time Manning directly admitted leaking hundreds of thousands of pages of material to the anti-secrecy website WikiLeaks and detailed the frustrations that led him to do it.
The slightly built soldier read from a 35-page statement for more than an hour. He spoke quickly and evenly, showing little emotion even when he described how troubled he was by what he had seen.
The judge accepted his plea to 10 charges involving illegal possession or distribution of classified material.
Manning was allowed to plead guilty under military regulations instead of federal espionage law, which knocked the potential sentence down from 92 years. He will not be sentenced until his court-martial on the other charges is over.
He has said he did not believe the release of the information he downloaded onto a thumb drive would harm the US.