War service: Western Front

Embarked Adelaide, 9 June 1916; disembarked Marseilles, France, 20 July 1916, for onward travel to England.

Appointed Lance Sergeant, 20 October 1916.

Proceeded overseas to France, 25 November 1916.

Promoted Sergeant, in the field, 21 January 1917.

Detached to General Headquarters Small Arms School, 21 June 1917; rejoined 43rd Bn, in the field, 1 August 1917.

Appointed 2nd Lieutenant, 18 August 1917.

Detached to School of Instruction, 29 September 1917; rejoined Bn, in the field, 3 November 1917.

Detached to Sniping School, 29 November 1917; rejoined Bn, in the field, 17 December 1917.

Promoted Lieutenant, 24 November 1917.

On leave to England, 8 January 1918; rejoined Bn, in the field, from leave, 24 January 1918.

Detached to Musketry School, 26 January 1918; rejoined Bn, in the field, 18 February 1918.

Detached to Sniping School, 23 February 1918; rejoined Bn, in the field, 30 April 1918.

Wounded in action, 26 May 1918 (gassed), and admitted to 9th Australian Field Ambulance; transferred to 53rd Casualty Clearing Station, 28 May 1918; to 55th Casualty Clearing Station, 28 May 1918; to Ambulance Train, 2 June 1918, and admitted to 1st General Hospital, Etretat, 2 June 1918; discharged to Base Depot, Havre, 20 June 1918; rejoined Bn, in the field, 26 June 1918.

Detached to 9th Training Bn, England, 28 July 1918. On Command, Sandown Gas School, 9 September 1918: attended 55th Course on Defensive Measures Against Gas, 9-18 September 1918; qualified 1st Class.

Granted leave of absence with pay and subsistence allowance of 10/- per diem, 1 February-31 March 1919: Non-Military Employment, in order to obtain experience of wool handling at Technical College, Bradford, Yorkshire, and with firms in Bradford. Granted extension of leave with pay and subsistence, 1 April-31 May 1919: Non-Military Employment, to attend wool classing course, Bradford Technical College. Further extension granted1 June-30 July 1919: work experience with J.S. Cowling, Bradford. Report from employer, 30 September 1919, stated: 'Lieut. Coats completed a course in wool sorting and classing. He was most industrious and keen, and certainly learnt a good deal and made the best of his opportunities.'

Marched into No 2 Group, Sutton Veny, 1 August 1919, on expiration of NME leave.

Commenced return to Australia on board HT 'Ascanius', 23 September 1919; appointment terminated (discharged), Adelaide, 30 December 1919.