Soldiers must be held accountable for their actions in the line of duty. To think otherwise is to invite Nazi-like thinking, to invite disaster.
That being said, the responsibility rests on the shoulders of the politicians who put those brave souls in situations where their honor may be impuned by poor decisions made in haste, or in the heat of battle. A democratic republic has no business fighting protracted wars, being involved in unconstitutional police actions and nation building. This invites disaster on every level.
Ultimately, it falls on us, the people, the voter, the citizen, first and foremost to raise our children with honor, and hold ourselves to that honor; and second, to elect men of courage and integrity to office.