[Stoat]

It was my belief that Aussie SAS troopers had been in Afghanistan since almost the beginning.

I'm sure that they have been; the article is making the distinction here of "Front Line" soldiers.

[Oztrich Boy]

For the SAS the frontline is "back there somewhere"

I think it's actually a case of the reporter not knowing what a "gun line" is.

It will be the first time Australians have manned a gun line on operations since Vietnam in 1973.