That one Australia meme everyone knows, the trick here is to B-line nuclear weapons and force a civil war where you can drop the bomb on the enemy in your territory. Alternatively, you can hope for a strong Japan that will invade you. Either way, make sure you have a good enough air...
You should be able to gain independence before the end of the war, through war contribution and the autonomy focus. You need a decent war score because you gained cores on east Germany, you need your old cores and the eastern German provinces to get the achievement. 1.11 简单 Habsburgs. ...