There's truth to the Madness of Max

The wiki says Australia was worried about "populate or perish" after WWII of a resurgent Japanese navy. I say that's secondary to a dominating Soviet nuke presence on the UK. Instead of rebuilding in a confined area, send some populace to the other side of the world: timezone advantage.

Think Mad Max.

http://en.wikipedia.org/wiki/Immigration_to_Australia
http://en.wikipedia.org/wiki/Post-war_immigration_to_Australia