Today is the 70th anniversary of Australia's entry into the conflict which is now known as World War 2.
At the time Prime Minister Menzies explained the reasons in a broadcast.
Here's what he said. I've emphasised the key words:
It is my melancholy duty to inform you officially that in consequence of a persistence by Germany in her invasion of Poland, Great Britain has declared war upon her and that, as a result, Australia is also at war.
No harder task can fall to the lot of a democratic leader than to make such an announcement.
Great Britain and France with the cooperation of the British Dominions have struggled to avoid this tragedy. They have, as I firmly believe, been patient. They have kept the door of negotiation open. They have given no cause for aggression.
But in the result their efforts have failed and we are therefore, as a great family of nations, involved in a struggle which we must at all costs win and which we believe in our hearts we will win.