Major Douglas James Stirling Armstrong was the son of Dr William Hunter Stirling and Beatrice Joan Armstrong, of Glasgow.
22 May 1840 Temporary Assistant Surgeon Ordnance Medical Department.
15 Apr 1841 Promoted Assistant Surgeon Ordnance Medical Department, vice Assistant Surgeon William Richardson.
Malta Mar 1847 Arrived at Malta.
1 Apr 1854 Surgeon Ordnance Medical Department.
22 May 1860 Surgeon Major Royal Artillery.
11 June 1861 Exchanged with Surgeon Major Thomas Llewellyn Nash 2nd/21st (Royal North British) Fusiliers Regiment of Foot.
7 Mar 1865 Appointed Staff Surgeon Major. The subsequent vacancy in 21st Foot was filled by Surgeon William Stewart 18th Foot, while Staff Surgeon James Henry Lewis became surgeon 18th Foot vice Stewart.
1866–67 Served in Bengal.
1868 On duty in Liverpool.
Malta 9 June 1869 Arrived from England on appointment.
Malta 1 Jan 1870 On duty at Forrest Hospital St Julians. Detachments of infantry occupied the barracks and huts at Pembroke Camp for the annual instruction in musketry from 1 January to 3 March, and from 5 October to 31 December 1870. The sick from the camp were admitted to Forrest Hospital (Spinola Palace) St Julians.
Between 1 January and 3 March 1870, Forrest Hospital was under medical charge of Staff Surgeon Major Mackintosh. On 3 March, the hospital was transferred to 87th Regiment for the summer season. It was retransferred and opened as a detachment hospital on 5 October.
Malta 3 Mar 1870 On duty at the General Hospital Valletta.
Malta 1871 On duty at The Valletta Hospital. Resident at 65 Strada Brittanica Valletta.
Malta 12 May 1872 On duty at the Forrest Hospital prior to leaving Malta.
11 Sep 1872 Retired to half-pay with the rank of surgeon major having completed 32 years service on full pay.
5 Sep 1890 Died at Malta of heart disease aged 72 years. Was buried on 7 September at Ta' Braxia Cemetery Pieta. His widow settled at Sliema Malta.
- Entry No: 4631. Johnston W. Roll of Commissioned Offices in the Medical Service of the British Army. Vol 1 (20 June 1727-23 June 1898), Aberdeen (1917).
- Biographical details of Medical Officers of the British Army on full pay (1826–1840).
- TNA:CO 158/223, Returns of the General and Staff officers of the hospitals attached to the Forces in Malta (April–July 1870).
- Succession Book Vol 2 (1 May 1846). Returns of service of medical officers in the Regular Army.
- TNA:CO 158/218 Malta Original Correspondence, Returns of Staff Officers Malta Garrison (January–May 1869).