Former comrades of Ben Roberts-Smith reported allegations of war crimes and bullying, but were initially brushed off by a superior who said it was "way above his head", one of the men has told a court.
The SAS soldier - codenamed Person 18 - also said he was later sent anonymous letters threatening him if he didn't retract his evidence to investigators about alleged wrongdoing by Australian forces in Afghanistan.
Person 18 was called to give evidence in a defamation trial launched by Mr Roberts-Smith, who is suing several newspapers over reports claiming he committed war crimes and several murders in Afghanistan between 2006 and 2012.
The Victoria Cross recipient vehemently denies the allegations reported by The Age, The Sydney Morning Herald and The Canberra Times, but the publications are relying on truth as a defence.
Person 18 told the court that around the end of 2012 he was drinking with a friend - codenamed Person Four - when he became upset and told him "something very bad" happened on a recent mission in the Darwan province.
Person Four claimed he saw Mr Roberts-Smith kick a detainee over a cliff.
Ben Roberts-Smith then told another soldier to "go down and sort it out," Person 18 said he was told.
Having grown sick of watching friends break down over incidents in Afghanistan, Person 18 told the court he, Person Four and two others soon arranged a meeting to discuss their concerns with their regimental sergeant major.
But Person 18 told the court the then-regimental sergeant major wasn't very receptive to the conversation.
"His response was, it was out of his hands, it was way above his head, and he honestly didn't know what to do with it," Person 18 said.
However the next year a new regimental sergeant major called the four men back for another meeting, which went for well over an hour as the group covered a list of topics.
At least one of the men spoke about bullying, and Person Four "broke down" as he again recounted the alleged cliff kick.
It wasn't the last time Person 18 spoke out about allegations of wrongdoing by Australians in Afghanistan, he told the court.
He gave evidence to a secret inquiry probing the allegations in 2018, but within days received a threatening letter in the mail.
"You and others have colluded to tell lies to the media and before the inquiry," Person 18 said letter read.
"It also stated that I had till the end of the month to change my statement, otherwise I'd go down.
"(It was) signed off, as a friend of the regiment."
The author, who had the soldier's personal details, said they had extensive knowledge of his military history, he said.
"The threat I took seriously. I had a concern for my own safety and that of my family's."
Person 18 reported the incident and the letter was given to the Australian Federal Police.
Mr Roberts-Smith has denied he wrote the letter, as reported by the newspapers, but the court last week heard from a private investigator - and former friend of the VC recipient - who admitted posting the letters to Person 18 on his behalf.
In hours of evidence, which will continue on Monday, Person 18 also told the court he'd heard Mr Roberts-Smith admit he had "blooded a rookie" after a 2009 mission to a Taliban compound, nicknamed Whiskey 108.
The phrase references a junior soldier getting their first kill in action.
"I didn't know what they were talking about at the time," Person 18 said.
Mr Roberts-Smith has been accused of murdering a detained Taliban fighter - whose prosthetic leg was later used by SAS soldiers as a drinking vessel - and of ordering Person Four execute to another.
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