[3][4] After the declaration of war in August 1914, the New Zealand government sent a small contingent of medical staff to Samoa to take over the hospital at Apia.

As the war progressed and the number of casualties increased, it became apparent that more medical personnel were required to treat them.

James Allen, Minister of Defence, offered to send medical personnel to a stationary hospital in Egypt, including eight officers and 50 nurses.

New Zealand medical personnel went on to serve in Samoa, Egypt, Palestine, Gallipoli, France, Belgium, Serbia and Great Britain.

2 General Hospital came under the control of the New Zealand Expeditionary Force in April 1916, and was located in the requisitioned 15th century Mount Felix estate until mid-1919.

[3] As part of the 2nd New Zealand Expeditionary Force, three General Hospitals, three Field Ambulances, and a Convalescent Depot were dispatched to the Middle East (and 1 General Hospital and 5 Field Ambulance to the United Kingdom with the Second Echelon, temporarily) along with the remainder of the force.

JOHG, in turn, in 2017 was superseded and the Deployable Health Organisation (DHO) was formed and its Headquarters is based in Linton Camp.

The DHO forms an integral part of the Joint Services Group (JSG) which is Headquartered in Trentham Camp.

After the unit has disembarked, it was deployed to Brockenhurst in the New Forest where it took over a hospital originally built for an Indian Division.

Most gain overseas operational experience with the NZDF within a short time and become proficient and experienced across a wide range of pre-hospital environments.