 Australia's defensive doctrine saw a fierce campaign fought along the Kokoda track in New Guinea.This campaign sought to further stretch Japanese supply lines, preventing the invasion of the Australian mainland until the arrival of fresh American troops and the return of seasoned Australian soldiers from Europe.This can be seen as a variant of the war of attrition strategy, where the defender—out of necessity—had to hold the aggressor at a semi-static defensive line, rather than falling back in the face of superior numbers.