If one country plays host to the armed forces of another, it has either been invaded or invited the second country in.
If the latter, this is indicative of some level of inadequacy on the part of the first country; an inability to fully take care of itself — the classical colonial situation, in which the superior country offers an inferior one “protection” from some third power presenting a threat.
Does Australia need protection? The northern coast of Australia was attacked during World War II, so the nation is clearly vulnerable to a military offensive.