The Anzac tradition—the ideals of courage, endurance and mateship that are still relevant today—was established on 25 April 1915 when the Australian and New Zealand Army Corps landed on the Gallipoli Peninsula.
It was the start of a campaign that lasted eight months and resulted in some 25,000 Australian casualties, including 8,700 who were killed or died of wounds or disease.
The men who served on the Gallipoli Peninsula created a legend, adding the word ‘Anzac’ to our vocabulary and creating the notion of the Anzac spirit.
In 1916, the first anniversary of the landing was observed in Australia, New Zealand and England and by troops in Egypt. That year, 25 April was officially named ‘Anzac Day’ by the Acting Prime Minister, George Pearce.
By the 1920s, Anzac Day ceremonies were held throughout Australia. All States had designated Anzac Day as a public holiday. In the 1940s, Second World War veterans joined parades around the country. In the ensuing decades, returned servicemen and women from the conflicts in Korea, Malaya, Indonesia, Vietnam and Iraq, veterans from allied countries and peacekeepers joined the parades.
During the 1960s and 1970s, the number of people attending the ceremonies fell as Australians questioned the relevance of Anzac Day. However, in the 1990s there was a resurgence of interest in Anzac Day, with attendances, particularly by young people, increasing across Australia and with many making the pilgrimage to the Gallipoli Peninsula to attend the Dawn Service.
The following text is from the Australian War Memorial website:
The Dawn Service observed on Anzac Day has its origins in an operational routine which is still observed by the Australian Army today. The half-light of dawn plays tricks with soldiers' eyes and from the earliest times the half-hour or so before dawn, with all its grey, misty shadows, became one of the most favoured times for an attack. Soldiers in defensive positions were therefore woken up in the dark, before dawn, so that by the time the first dull grey light crept across the battlefield they were awake, alert and manning their weapons. This was, and still is, known as "Stand-to". It was also repeated at sunset.
After the First World War, returned soldiers sought the comradeship they felt in those quiet, peaceful moments before dawn. With symbolic links to the dawn landing at Gallipoli, a dawn stand-to or dawn ceremony became a common form of Anzac Day remembrance during the 1920s; the first official Dawn Service was held at the Sydney Cenotaph in 1927. Dawn services were originally very simple and followed the operational ritual; in many cases they were restricted to veterans only. The daytime ceremony was for families and other well-wishers, the Dawn Service was for old soldiers to remember and reflect among the comrades with whom they shared a special bond. Before dawn the gathered veterans would be ordered to "stand to" and two minutes of silence would follow. At the end of this time a lone bugler would play the "Last Post" and then concluded the service with "Reveille". In more recent times families and young people have been encouraged to take part in dawn services, and services in Australian capital cities have seen some of the largest turnouts ever. Reflecting this change, the ceremonies have become more elaborate, incorporating hymns, readings, pipers and rifle volleys. Others, though, have retained the simple format of the dawn stand-to, familiar to so many soldiers.
See: Gallipoli and the Anzacs website