A communications breakdown was to blame for the "friendly fire" deaths of two British soldiers in Iraq in March 2003, an Army inquiry has found.
The two men died five days after the start of the Iraq war
A Royal Tank Regiment Challenger 2 tank fired on another occupied by Cpl Stephen Allbutt, 35, and Trooper David Clarke, 19, both from Staffordshire.
The first tank lacked information about other British units on the outskirts of Basra, the Army board of inquiry found.
No soldiers would be charged over the deaths, the Ministry of Defence said.
That decision was taken by the independent Army Prosecution Authority, which was asked to consider the case by the Royal Military Police's Special Investigation Branch.
The full report, to be published on Friday, will say the Royal Tank Regiment tank had become disoriented at the time of the incident, the MoD said.
The inquiry said, among contributing factors, the "location of the friendly tanks ... should have been more generally known".
The crew of the tank which fired were "slightly disorientated" about their own position.
"They fired into what they thought was an enemy position," an MoD spokesman said.
They fired a second round which hit Cpl Allbutt's tank.
The report will make recommendations on better dissemination of critical information on the battlefield and improved training.
This would include teaching soldiers what different types of armoured vehicles look like and knowing when to fire.
Cpl Allbutt was from Stoke-on-Trent and Trooper Clarke from Littleworth, both were from the Queen's Royal Lancers.
Two other soldiers were seriously injured in the incident.
The MoD spokesman said the incident happened when the main threat was thought to be enemy tanks and infantry armed with rocket-propelled grenades.
"It was in the war fighting phase, with all the pressure and difficulties associated with an operational environment."
Junior defence minister Don Touhig said: "The [board of inquiry] is not there to apportion blame, but to establish the facts and make recommendations in an attempt to stop such a tragedy happening again."
He said he hoped the report would give the families of the soldiers "a much better understanding of this awful tragedy".
Although both men's families say they have had to wait too long to get answers, Debbi Allbutt, Cpl Allbutt's widow, said on Thursday she was happy with the findings.
She said: "I am pleased...I do think it is very much in depth.
"I have no problems with the report at all, they have given us all the information that we needed, all the answers."