The roots of revisionism
As Ros points out in a comments thread below, the starting point for Stephen Barton’s revival of the Brisbane Line appears to be the work of Dr Peter Stanley, Principal Historian, Australian War Memorial, who has denied the ‘myth’ of a Japanese invasion, and criticised Curtin’s rhetoric on the subject. He relies almost exclusively on evidence that “.. there was no invasion plan. The Japanese never planned to make Australia part of its Co-Prosperity Sphere.” His main focus is criticism of statements by the Curtin government suggesting the opposite.
There’s a crucial ambiguity here, both in Curtin’s rhetoric and in Stanley’s response. If Port Moresby had fallen, and the Australian forces in PNG been destroyed or captured (and if the Battle of the Coral Sea had gone the other way), the Japanese would surely have pushed on to occupy ports and airfields in Northern Australia to deny their use to the Allies, and, if possible, knock Australia out of the war altogether. Such a move would have strengthened their position in the Pacific, and freed forces to fight elsewhere. On the other hand, an attempt to conquer the entire country and incorporate it into the Co-Prosperity Sphere would indeed have overstretched the Japanese capacity beyond its limits.
When Curtin referred to Kokoda as saving Australia from invasion, he was certainly justified, but, in motivating the war effort, it didn’t hurt to blur the difference between a partial occupation and a total conquest. By contrast, it’s hard to see how Stanley is serving the cause of historical accuracy by failing to make this crucial distinction.
Stanley can’t be blamed for the use people like Barton are making of his work, but he can certainly be criticised for intellectual sloppiness in his analysis.