A panel of experts told the commission "lazy leadership" in defence had encouraged alienation of anyone in the service who was struggling, or somehow different, including women.
Sociologist James O'Connor said turning the tribe on one of their own was a practice used to encourage ferocious group loyalties, based on the belief that it improved "combat effectiveness". But it had a devastating impact on the target.
"The desperate dark side of that is ... this idea that you don't rat on fellow soldiers, you don't go jack," Mr O'Connor said.
"What this means is most things stay in house. It becomes impossible for the victim to speak out and that leaves them in a deeply vulnerable space."
Veteran and sociologist Ben Wadham told the commission that when entering the service, recruits had to "renounce their identity" and enter a "very masculine, insular" world.
He said while there were many positives to living in such a strongly bonded community, "if you fall on the wrong side of it, it comes crashing down on you".
"There's a dark side to the military ... it's often portrayed as a few bad apples but indeed it's a systemic part of the military system," Assoc Prof Wadham said.
Zac E. Seidler, a clinical psychologist at Melbourne University, said repeated inquiries had failed to make a dent in the defence force culture.
"The stripping away of identity must change," he said.
"We don't need to create these warriors that are devoid of emotionality."
Commissioners also heard evidence from Nikki Jamieson, the mother of a 21-year-old army private who suicided in 2014.
She said her son, Private Daniel Garforth, joined the army as 19-year-old, a "very cheeky chappy ... very much a class clown".
He suffered "endless torment" when he was targeted by members of his chain of command, but his loyalty to his defence tribe, she said, had ultimately been his "Achilles heel".
It added to his distress when the army later turned on him, dismissing his bullying complaints and casting him as a "malingerer".
"These feelings of betrayal ... spiralled his mental health further ... heightened his feelings of guilt and shame at not being good enough."
There had been numerous red flags Mr Garforth was in serious trouble but at no point did the army contact his family or any external organisations for help, the commission was told.
"He was described as catatonic by the very chain of command that was threatening him ... he told people he was fearful of going to work, he was withdrawing from friends and colleagues," Ms Jamieson said.
A day before his suicide Daniel punched a wall in a fit of rage and had to be taken to hospital.
In his suicide note the next day he said he could no longer bear being ridiculed.
Since her son's death Ms Jamieson has become a suicidologist and expert on moral injury and suicide in the defence community.
She said the archaic indoctrination and training was a "huge problem" in the defence force.
Earlier in the day senior counsel assisting the commission, Kevin O'Connor SC, said the true rate of suicide among serving defence members and veterans is likely to be higher than surveys reported by the Department of Defence and Veterans' Affairs.
The royal commission is due to produce an interim report by 11 August next year and a final report by 15 June, 2023.
It comes as the federal government said reform of support programs for Australian veterans will not be delayed as the royal commission takes place
Veterans' Affairs Minister Andrew Gee has provided the fifth annual statement on veterans and their families, which outlines the government's key support priorities, in parliament on Monday.
He said work was being done to better assist their transition to civilian life, improve claims processing and harmonise legislation to make it easier to understand and access compensation.
For the first time, the 2021 census asked if respondents had ever served in the Australian Defence Force.
Mr Gee said the data collected would show the government a clearer picture of how many veterans there are in Australia, where they live and other key demographics to better target support.
The statement came on the same day the royal commission into defence and veteran suicide began its public hearings.
Mr Gee said the testimonies would be a "watershed" moment for the country.
"Mistakes and failings must be acknowledged. Truth must be told. Action must be taken," he said.
More needed to be done to destigmatise mental health issues and stop bullying, abuse and sexual assault in the ADF.
"I am determined to address the high rates of suicide amongst the ADF and veteran community," Mr Gee said.
"They have given us their best and in return it's only right that we give them our best."
Readers seeking crisis support can contact Lifeline on 13 11 14, the Suicide Call Back Service on 1300 659 467 and Kids Helpline on 1800 55 1800 (for young people aged up to 25). More information and support with mental health is available at Beyond Blue.org.au and on 1300 22 4636.
Embrace Multicultural Mental Health supports people from culturally and linguistically diverse backgrounds.