Who ever said war was Hell was wrong. He was glad to serve his country. He knew his alchemy was perfect for fighting on the front lines.
It wasn't until it was over that things went to Hell for him. He sat on the same concrete bench staring at the wooden contraption that should keep him from transmuting the guards into something deadly.
The guards loved to tell him about all Mustangs successes, they were sure it bothered him.
If they only knew he cataloged each occasion, and promised himself that he would be free one day.
Why should Mustang be free and have a notable record ,while Kimblee sat alone in cell.
Kimblee knew the truth Mustang was just as guilty as he was.