From the age of 12 all males in New Zealand received military training. In 1911 New Zealand formed a 25,000, part-time national militia. Most of the men who volunteered to join the New Zealand Expeditionary Force (NZEF) in August 1914 came from this Territorial Army.

Under the command of General Godley, the NZEF joined with the Australian Imperial Force in Australia. The two forces were sent to Egypt for training with British weapons. It was decided to put Australian and New Zealand forces together to form the Australian and New Zealand Army Corps (ANZAC). Some were used to defend Suez but most of them were sent to the Gallipoli Front. The ANZACs suffered over 33,600 losses (over one-third killed) by the time they were ordered to withdraw in January 1916. The New Zealand troops were then transferred to the Western Front in France.

During the First World War over 124,000 New Zealanders, almost 10 per cent of the population, joined the army. Of these, 100,000 served overseas and the high percentage who served on the front-line is reflected in the fact that they suffered 58,000 casualties, including 17,000 men killed.