Treloar was appointed the director of what eventually became the AWM in 1920, and was a key figure in establishing the Memorial and raising funds for its permanent building in Canberra.

Treloar also participated in his school's cadet unit, and believed that the military offered a means to follow his ambition for a career in a field other than small business.

[2] On 16 August 1914, shortly after the outbreak of World War I, Treloar enlisted in the First Australian Imperial Force (AIF) and became a staff sergeant working for White in the headquarters of the 1st Division.

[10] Treloar's older brother William also enlisted in the AIF during April 1915, and was one of the few members of the Mesopotamian Half Flight to survive captivity after being captured by Turkish forces.

1 Squadron AFC in Egypt and served as its equipment officer until July 1916, when he was transferred to France to become White's confidential clerk in the headquarters of I Anzac Corps.

At this time the Section comprised four enlisted soldiers and occupied two rooms in the British Public Record Office's (PRO) building in London.

[18] To this end, Treloar met with many of the officers responsible for units' war diaries and frequently provided written advice and feedback on the quality of the records submitted to the Section; these methods had previously been used by the Canadian military.

[19] Treloar also sought to motivate relevant personnel by demonstrating that the diaries were valued and would be important in ensuring that their unit received recognition for its achievements after the war.

Its tasks increased further in September when it took over responsibility for supervising the official war artists as well as producing and keeping records of non-official publications such as regimental magazines.

[21] From November 1917 until August 1918 the war correspondent Henry Gullett commanded the AWRS subsection in Cairo; in this role he reported directly to Treloar.

[10][25] Treloar was appointed a Member of the Order of the British Empire (MBE) on 3 June 1918 for "services in connection with the war" and was promoted to major in December 1918.

He has been criticised for not delegating this work, but it reflected a desire to ensure that inaccuracies in the captions did not detract from other aspects of the museum given that they would be closely read by veterans and other knowledgeable visitors.

For instance, in 1921 he wrote to all the Australian Victoria Cross recipients of World War I or their families to ask that they donate their wartime diaries or other personal items.

[41] Taking up an idea of Bean's, Treloar oversaw the development of several dioramas depicting key Australian battles of the war and engaged professional artists to make the models.

[45] During its early years the AWM existed in a parlous state, and Treloar raised funds and advocated construction of a permanent building to house its records and collection of artefacts.

To this end, Treloar established a sales section in the museum in 1921 and recruited salesmen to sell books, reproductions of artworks and photographs as well as surplus items from the collection such as German helmets and rifle cartridges.

[46] The Government was slow to commit to building a permanent home for the museum's collection, however, and Treloar considered resigning in July 1922 to take up a position in the Department of Immigration.

An architectural competition was subsequently held, and Treloar was responsible for selecting the final designs to be considered after the judging panel had reduced the number of entries from 69 to 29.

As well as selling guidebooks, reproductions of artworks and surplus items, the Memorial raised substantial amounts of money from placing an admission fee on Will Longstaff's painting Menin Gate at Midnight when it went on display in 1929.

[57] In 1931 Treloar ensured that the Memorial took over responsibility for the publication and distribution of the Official History of Australia in the War of 1914–1918 when the project suffered financial difficulties due to poor sales.

To achieve this, he implemented tight internal controls over the department's procedures and information dissemination functions and instructed subordinates to not defend the government from criticism.

[68][69] He remained the departmental secretary after Gullett was moved to a different ministry in March 1940, but lost status when Keith Murdoch was appointed to the new position of Director-General of Information in June that year.

[23] Treloar regained full control of the DOI in December that year when Murdoch resigned, though its photographers were still mainly tasked with taking publicity photos.

[73][74] At some point in 1940 or early 1941, Treloar requested that he be appointed to command the War Records Section, which formed part of the Second Australian Imperial Force's administrative headquarters.

[75] Conditions in North Africa proved more challenging than those in World War I, however, as the combat was fast-moving and the Australian troops felt less motivation to collect artefacts than those of the First AIF.

While MHIS teams accompanied the 6th and 7th Divisions when they departed the Middle East in early 1942, Treloar remained in Egypt until May that year as he was initially unable to secure space on board ships for the Section's extensive collections.

[82] The MHS continued the MHIS' role of facilitating the production of high-quality paper records and photographs of the war and collecting the resulting documents and images.

Treloar's editorial role came on top of his full-time duties as head of the MHS and was one of the main causes of his exhaustion and anxiety in the final years of the war.

[95] His funeral was held two days later at Reid Methodist Church in Canberra, and he was subsequently buried in the returned soldiers section of Woden Cemetery.

Bean also personally reviewed the Memorial's collection of World War I artefacts during 1952 and 1953, and found that the register of these items was inadequate and it was not possible to locate many of them.