Former commander of US troops in Iraq Lt Gen Ricardo Sanchez has been cleared over abuses at Abu Ghraib jail in Iraq.
The images shocked the world
A new inquiry found no evidence of wrongdoing by Gen Sanchez and three of his top aides, US officials say.
The US army inspector general's report says only Brig Gen Janis Karpinski, commander at the jail, has been found guilty and reprimanded over the abuse.
Pictures of Iraqi inmates abused by US soldiers caused an outcry last year. Five US soldiers have been convicted.
The Pentagon has held nine major inquiries into the Abu Ghraib prisoner abuse scandal, with two more to come.
US Defence Secretary Donald Rumsfeld is being sued by two civil liberties group for allegedly authorising torture and then failing to stop it.
The results of the inquiry have surfaced in the week before the first anniversary of the publication of the first photographs showing US forces sexually humiliating and physically abusing Iraqi prisoners.
The scandal at the jail on the outskirts of Baghdad triggered international criticism of the US.
Since then, numerous cases of alleged abuse have come to light at US facilities in Afghanistan and at Guantanamo Bay.
Rights groups unhappy
Gen Sanchez, who commanded US troops in Iraq until the summer of 2004, authorised tougher interrogation techniques during a brief period in September 2003 during which the abuses are alleged to have been carried out.
But the inspector general's report says it has found no evidence that he was guilty of dereliction of duty.
Among the mitigating circumstances it lists:
- Initially, US military command was short of senior officers
- Gen Sanchez had to focus on an upsurge of insurgent violence
- He was under pressure to find ousted Iraqi leader Saddam Hussein.
Gen Sanchez's three top aides, including his deputy, Gen Walter Wojdanowski, have also been exonerated, the US officials said.
But Brig Gen Karpinski has been sent a written reprimand and relieved of her command.
In the past, she has vowed to fight any measures against her.
Gen Sanchez authorised tough interrogation techniques
She told the BBC last year that had been made a "convenient scapegoat" for abuse ordered by others at the top, including Gen Sanchez.
Human rights groups have criticised the latest findings, full details of which are to be made public after members of the US Congress are briefed.
"What this decision unfortunately continues is a pattern of exoneration and indeed promotion for many of the individuals at the heart of the torture scandal," said Amnesty International spokesman Alistair Hodgett.
"It only serves to underscore the desperate need for an independent investigation that will scrutinize the policy decisions and the individuals who made and implemented them in a manner that will expose the truth," Mr Hodgett told Reuters news agency.