Dive Bombers allow German Fighters to attack on Round 1 at 5 or less. However it ONLY applies to land battles and ONLY if no defending fighters are present.
Dug-In Defenders for Japan allow infantry defending on islands (as defined as a land mass completely circumscribed by ONE sea zone) to defend at 3 or less on round 1.
Australia, Japan, Madagascar, Greenland, etc are NOT considered islands because they have more then one sea zone.
This was answered when America had Island Bases and these were determined not to be islands because it would allow fighters to extend their range artificially more so then just the island base. (You could fly into a sea zone, over the island free and be in the next sea zone without using a movement point.)