ANZAC (abbreviation for Australian and New Zealand Army Corps) first referred to a body of Australian and New Zealand troops who fought in World War I at Gallipoli, in the Middle East and on the Western Front.

Within Australasia the Anzacs came to stand not just for the troops in World War I, but for Australian and New Zealand soldiers in time of war more generally. Anzac Day is annually celebrated in memory of those soldiers who died in war. It is celebrated each year by both countries on April 25, the date of the first landing at Gallipoli in 1915 on a beach which was subsequently to become known as Anzac Cove. (It is similar to days such as Veterans Day, Armistice Day or V-E Day celebrated in other countries.)

Anzac Formations

The original formation (the Australian and New Zealand Army Corps), which served at Gallipoli, comprised the Australian 1st Division and the New Zealand and Australian Division. The three Australian and one New Zealand mounted brigades were employed as infantry with the ANZAC during the Gallipoli campaign.

The Anzac Mounted Division (originally the Australian and New Zealand Mounted Division) fought as mounted infantry throughout the Middle East, including Egypt, the Sinai (Romani, Magdhaba and Rafa) and Palestine (First and Second Battle of Gaza, Beersheba, Jerusalem, Jericho, Es Salt, Megiddo and Amman) and Syria.

On the Western Front, Anzac formations participated in many battles. Australian and New Zealand Divisions were involved in a number of the Battles of the Somme, July to November, 1916, while components of British corps but it was only during the Battle of Pozieres, 23rd July 1916, that an Anzac formation participated. This was 1st ANZAC (Australian 1st, 2nd and 4th Divisions).

In the Arras Offensive (April-May 1917) the 1st ANZAC was involved in combat around Bullecourt. At various times this formation contained the Australian 1st, 2nd, 4th and 5th Divisions.

2nd ANZAC (Australian 3rd and 4th Divisions, New Zealand Division plus the British 25th Division) fought in the Battle of Messines, July 1917, which was a prelude to an Allied offensive from the Ypres salient.

In the middle and closing stages (August to November, 1917) of the Third Battle of Ypres, also called the Battle of Passchendaele, Anzacs fought in the following attacks:

;the Battle of Menin Road:1st ANZAC (Australian 1st, 2nd, 4th and 5th Divisions) ;the Battle of Polygon Wood:1st ANZAC (Australian 1st, 2nd, 4th and 5th Divisions) ;the Battle of Broodseinde:1st ANZAC (Australian 1st and 2nd Divisions), 2nd ANZAC (Australian 3rd Division and the New Zealand Division) ;the Battle of Poelcapelle:1st ANZAC (Australian 1st and 2nd Divisions) ;the First Battle of Passchendaele:1st ANZAC (Australian 4th and 5th Divisions), 2nd ANZAC (Australian 3rd Division and the New Zealand Division) ;the Second Battle of Passchendaele:1st ANZAC (Australian 1st, 2nd and 5th Divisions)

At Villers-Bretonneux, in the 1918 First Battles of the Somme, the ANZAC designation ceased to be used to represent an army corps containing Australian and New Zealand Divisions. 1st ANZAC was renamed the Australian Corps (and comprised the Australian 4th and 5th Divisions at the time).

During the Vietnam War, two companies from the Royal New Zealand Infantry Regiment operated as part of the 4th Battalion of the Royal Australian Regiment (4RAR) which was then referred to as the 4RAR/NZ (Anzac) Battalion.