Donald Trump's claims allied forces including Australian troops "stayed ... a little off the front lines" in Afghanistan have drawn the ire of the RSL.
The veteran welfare organisation's national president Peter Tinley says the US president's remarks are factually wrong, historically ignorant and deeply offensive.
Some 47 Australian service personnel were killed in the almost 20-year conflict.
A further 261 were wounded among almost 40,000 Australians who served in the war between October 2001 and June 2021.
Mr Tinley said the facts spoke for themselves.
Australian forces were among the first coalition troops into Afghanistan following the September 11 attacks, he said.
"I know because I was there as Deputy Commander of the Special Forces Task Group in those opening months," Mr Tinley said.
"For two decades, Australians operated in Uruzgan Province, one of the most dangerous regions in the country."
Mr Trump provoked outrage in the UK after suggesting on Thursday that troops from NATO countries stayed away from the frontline in Afghanistan, with Prime Minister Sir Keir Starmer condemning the remarks.
In an interview with Fox Business Network, Mr Trump said he was not sure NATO would be there to support the US if and when requested.
"I've always said, will they be there if we ever needed them and that's really the ultimate test and I'm not sure of that," Mr Trump said.
"You know, they'll say they sent some troops to Afghanistan or this or that - and they did, they stayed a little back, a little off the front lines."
Mr Trump provoked outrage in the UK after suggesting on Thursday that troops from NATO countries stayed away from the frontline in Afghanistan, with Prime Minister Sir Keir Starmer condemning the remarks.
Mr Trump on Sunday morning posted a message on Truth Social praising the "great and very brave soldiers of the United Kingdom" and said they "were among the greatest of all warriors".
The online post came after a discussion between Mr Trump and Sir Keir about the issue on Saturday, UK officials said.
An angry Mr Tinley said Mr Trump's initial remarks demanded a show of Australian leadership.
"I call on the prime minister and the leader of the opposition to reaffirm, in the clearest terms, that Australia's service in Afghanistan was conducted with courage, professionalism and distinction," he said.
"The prime minister should call on President Trump to withdraw his comments and apologise to all those who served."
Mr Tinley said Australian troops "didn't stay a little back".
"They conducted offensive counter-insurgency operations, cleared Taliban strongholds, defused roadside bombs, mentored Afghan forces under fire, and fought in sustained close combat."
Four Australians were awarded the Victoria Cross, Australia's highest honour for battlefield gallantry in Afghanistan.
Among them, Corporal Cameron Baird was killed in action in 2013 after charging an enemy position three times to protect his mates.
Trooper Mark Donaldson ran through enemy fire to rescue a wounded interpreter and Corporal Daniel Keighran deliberately drew enemy fire away from wounded colleagues.
Mr Tinley said these were not the actions of men who "stayed behind the lines".
"To our veterans, I say I understand what you are feeling today. I feel it too," he said.
"To have your service dismissed so casually is a profound insult."