Robert Lindsay enlisted for war service on 18 May, 1916. He was 34 years old when he joined the AIF, single and a miner at Cootamundra, NSW. He had grown up in East Melbourne, however, with his parents, Matthew and Frances Lindsay, still iving at 30 Gipps St. 

He was sent for training to Victoria Barracks, Melbourne, before embarking on HMAT Ceramic A40 on 7 October, 1916, landing at Plymouth on 21 November.At this stage, he was with the 6th Reinforcements for the 45th Battalion. By then, the 45th Battalion had had extensive battle experience, including in the battles of Gueudecourt and Flers in November, 1916.

Robert Lindsay marched out from England with the 12th Training Battalion on 7 January, 1917, leaving for France on 16 January on board the Princess Victoria from Folkestone. The photograph in the files of the Australian War Museum, Canberra was from a personal collection, and marked 17 January, 1917, Belgium, but the 45th Battalion was not in Belgium until later in the year. Nor is there anything in his file to show that he played an instrument and the photo simply lists the names of those present, but does not identify their position in the picture.

On 19 January, Robert Lindsay was taken on strength in the field with the 45th Battalion. In May, the 45th fought at Bullecourt, part of the Ypres campaign. In June, they took part in the battle for Messines, and in late 1917, they were at Passchendaele. Robert Lindsay survived all these major actions, but on 22 November, was taken off the field sick with trench fever, first to the 12th Australian Field Ambulance station, then to the 3rd Australian General Hospital at Abbeville, France, before being sent back to England on 7 December to the 1st Birmingham War Hospital.

Trench fever was transmitted by body lice, something from which every soldier in the trenches had due to poor hygiene. Its symptons were a high fever, severe headaches, pain on moving the eyeballs and muscle soreness. Victims suffered from constant pain in the legs and recovery took a month or more. Once recovered, the patient would suffer recurrent bouts of fever. 

With all he had suffered, both at the front and in hospital, it is little wonder that Robert Lindsay had had enough. On 20 December, he went AWL from the hospital, returning drunk at 1 am on 27 December.  He was treated lightly, forfeiting only two days pay . On January 7, he was given two weeks leave and ordered to report back to Adminstrative Headquarters at Hurdcott on 21 January. From here, he was attached to the No.3 Command Depot, then on 16 April, sent to the Overseas Training Brigade at Deverill, Folkestone,and sent to the Overseas Training before returning  to France on 10 April, 1918.

The 45th Battalion was in the heat of the defence of Amiens, resisting the last great German offensive of the war. As the Germans moved towards the important rail junction at Amiens, the 45th fought at Villers-Brettoneux  in April and at Dernancourt, Messines and Ploegstaart Wood. 

Robert Lindsay, however,  fell ill again on 12 July 1918 and was sent to Le Havre, rejoining his battalion on 20 July. The illness is not specified in his war service record, but it could have been a return of trench fever or any other sickness. On 8 August, he would have been part of 'the black day for the German Army' when the allied troops defeated the Germans, forcing them back to the Hindenburg line. On that day, the 45th caputured 400 German prisoners, 30 Artillery pieces and 18 Machine guns. Their last major action was on 18 September around Le Veuier to seize the outpost that guarded the approach to the main defences of the Hindenburg Line. Tha Battalion was then placed 'out of the line' and finally disbanded on 2 May, 1919.

The war ended on 11 November, 1918, but it took monts to deal with clearing up of the battlefields and returning  the soldiers. Robert Lindsay was granted leave in the UK on 8 February, but returned to France on 18 February for duty with demobbing, rejoining his battalion on 1 March 1919. From here, he went back to England on 21 April, reporting to the No. 2 Group at Sutton Veny. He was finally returned to Australia on board the Port Napier on 12 May, 1919.

Nothing much is known of him after his return. There is one letter from him to the Defence Department, dated 12 April, 1943. At this time, he was living at 'Welwyn', Koroop, Victoria. It is imposiible to follow his life through the Electoral Rolls, because there are numerous Robert Lindsays. There is no record of him marrying.