Harold Lee was twenty-one years and five months when he enlisted at Melbourne on 7 July, 1915. He was a confectioner by trade and lived with his mother, Matilda Elizabeth Lee, a widowed dressmaker living at 9 Albert St., East Melbourne. After training with A Company, 10th Battalion at the Showgrounds in Ascot Vale,  on 26 November he was attached to the 13th Reinforcements of the 6th Battalion and left for Egypt on 29 December, 1915, on board HMAT Demosthenes A 64. Here the new recruits were taken on strength with the 6th Battalion and after  further training at Serapeum, proceed to join the British Expeditionary Force at Alexandria on 25 March, 1916.

From Alexandria, the 13th Reinforcements boarded the O.C. Transport Ballarat, landing at Marseilles on 30 March, 1916, and from there, moved to the front. Initially, they were in the 'nursery sector' at Fleurbaix, but were in the front line at Pozieres in July, 1916, losing 102 men. Harold Lee was not with them: on 17 March, he was transferred to the 1st Australian Division Pioneeer Battalion, the soldiers repsonsible for everything from digging trenches and dugouts, constructing duckboard paths, establishing communication lines, establishing food depots and many other tasks. On 30 June, however, he became ill and was sent to hospital suffering form broncho-pneumonia. The illness must have been severe, because on 27 July, he was sent back to England on H.S. Jan Breydel and admitted to the All Arms Military Hospital at Epsom. It was not until 13 October that he was released and marched in to the No. 3 Command Depot. From here he transferred to the No. 4 Command Deport at Wareham on 3 November. He stayed in England until the following year, when he was transferred on 25 March, 1917,  from the 1st Pioneer Battalion over to the 65th Battalion, marching in to Perham Downs from Wareham.

Harold Lee was again admitted ill to hospital on 27 July, 1917 and following discharge was sent to the Signal School at Hurdcott, marching back in to his battalion on 24 October, 1917. On 21  March, 1918, he returned to France, rejoining the 1st Pioneers. He did not stay long, because on 23 March, he was sent for duty with the 2nd Army Central School, though there is no note to say where it was situated. Here Harold Lee's army number was re-allocated and he became 4239B. He embarked for England on 4 January, 1919, he marched out for the return to Australia, setting out for home on 9 March, 1919, on board HT City of Poona from Southampton and landing in Melbourne on 14 May. He was officially discharged from further  service on 7 July, 1919.

It is difficult to trace what happened to Harold Lee after the war. The one glimpse of him is in the Electoral Roll of 1925, when he was living with his mother, Matilda Eizabeth Lee, at 10 Stafford St., Abbotsford and working as a labourer.