ANZAC Day falls on 25 April each year and it is one of Australia’s most important national occasions. ANZAC Day marks the anniversary of the first major military action fought by Australian and New Zealand forces during the First World War (WW1).

ANZAC stands for Australian and New Zealand Army Corps. The soldiers in those forces quickly became known as ANZACs, and the pride they took in that name continues to this day.
When the war broke out in 1914, Australia had been a federal commonwealth for only 14 years and its new Government was keen to build its reputation with other allied forces across the world. 
In 1915, Australian & New Zealand soldiers set out on a joint expedition to capture the Gallipoli peninsula in order to ensure allied navies could access the Black Sea. 
The Australia and New Zealand Governments' planned to capture Constantinople (now known as Istanbul), the capital of the Ottoman Empire and an ally of Germany. 
The ANZAC soldiers landed in Gallipoli at dawn on the 25th of April. Upon arrival, the soldiers met fierce resistance from the Turkish defenders and the campaign lasted for eight months.
More information about the ANZAC Day tradition can be found here.