In late 1915, he volunteered for service abroad with the New Zealand Expeditionary Force (NZEF) and was posted to the 2nd Battalion, the Otago Infantry Regiment.

His VC was the second to be awarded to a soldier serving with the NZEF during the war and was the first earned in an action on the Western Front.

[3] When the First World War broke out, Brown continued to work on his farm for a year but then sold it and volunteered for the New Zealand Expeditionary Force (NZEF) on 19 October 1915.

[4] He received his training at Trentham Military Camp and embarked for the Middle East in January 1916 with the Ninth Reinforcements.

[3] The newly formed New Zealand Division was training in Egypt and when Brown arrived, he was posted to the 2nd Battalion, Otago Infantry Regiment.

[4] After a period of rest, Brown's battalion moved back into the front line on the evening of 28 September.

It was to be one of the assaulting battalions involved in an attack to clear out a German trench system near Eaucourt L'Abbaye[13] as part of the Battle of Le Transloy that commenced on 1 October.

On the opening day of the battle, Brown was again involved in the seizing of a German machine gun post at a strongpoint that was holding up the advance.

In a letter to Brown's father, his battalion commander hoped that the recommendation would be upgraded to a Victoria Cross (VC).

[16] The senior leadership of the NZEF were slow to recognise Brown's gallantry and it was not until the officers of his battalion lobbied for a VC nomination that any progress was made.

[4] The citation read: For most conspicuous bravery and determination in attack when the company to which he belonged suffered very heavy casualties in officers and men from machine gun fire.

[Note 2] Arthur Foljambe, the 2nd Earl of Liverpool and New Zealand's Governor General, presented the VC to Brown's father in a ceremony at Oamaru on 30 August 1917.

[23] In 1919, as part of an effort to recognise men from North Otago who had been killed in the war, an oak tree was planted in his memory in Oamaru.