Announcing Australia's commitment to the war on 3 September 1939, Prime Minister Robert Gordon Menzies spoke the following, famous words that were broadcast on every national and commercial radio station in the country:

"Fellow Australians, 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."

As part of the British Empire, Australia was among the first nations to declare war on Nazi Germany and between 1939 and 1945 nearly one million Australian men and women served in what was going to be World War II. They fought in campaigns against the Axis powers across Europe, the Mediterranean and North Africa. In 1941, The Japanese Imperial Navy attacked Pearl Harbour and advanced into South East Asia. As a result, the Allied powers including Australia were at war with Japan as well.

During this period, the Australian mainland came under direct enemy attack for the first time in history, with Japanese bombing attacks on Northern Australia and an attack on Sydney Harbour by Japanese midget submarines. At the time of German defeat and Japanese surrender, 39,000 Australians had lost their lives and another 30,000 had been taken prisoner.