I hate historical inaccuracies, so I feel driven to correct them.
In 1915, the former Australian colonies had been an independent nation for fourteen years. The former colony of New Zealand had been independent for seven years.
Technically it was the ratification of the Statute of Westminster that formed the formal declaration of independence for the Old Dominions. This is New Zealand’s official interpretation so that dates our independence in 1947 and this interpretation pushes Canada’s independence to be 1931 and Australia in 1942.
A dominion is, strictly speaking, a self-governing dependent territory rather than an independent country.