Birthplace:
- Glasgow, Scotland

Birthdate:
- 17 October 1833

Nationality:
- Scottish

Height:
- 5 feet 11 inches

Family Background
- Finlay's father was John Finlay, a Justice of the Peace, Perthshire, Scotland

At Sandhurst:
- No

Foreign Languages:
- French and Hindustani

Career before Halifax:
- Ensign, 78th Highlanders, 14 February 1851 (purchase)
- Lieutenant, 22 December 1854 (purchase)
- Captain, 21st Foot, 10 September 1858 (non-purchase)
- to 78th by exchange, 4 November 1859

Medals & Awards:
- Medal and clasp (Persia)
- Medal and two clasps (Indian Mutiny)

Postings while in NS Command:
- 9 May 1869 to 22 June 1871
- to depot company in Scotland, 23 June 1871

Married:
- Mary Marcella Taylor, at Christchapel, Bayswater, London, 13 January 1863

Children:
- Isabella Marcella Buchanan (b. Aberdeen, 9 September 1864)
- Bertha Agnes (b. Edinburgh, 6 December 1867)

Career after Halifax:
- Brevet Major, 5 July 1872
- retired by sale of commission, 28 July 1873

Finlay's father, also named John, was the proprietor of Deanston House, Perthshire, and a Justice of the Peace of that county. The latter was the second son of one Kirkenan Finlay who made a fortune in Glasgow early in the nineteenth century, and acquired the estates of Castle Toward in Argylshire, and Woodhay in Surrey. The fact that John Finlay Sr. became a J. P. doubtless indicates that he enjoyed some status in his own right. Thus through his father and grandfather young John Finlay, later of the 78th, would have been familiar with the world of the Scottish and English landed classes.

Finlay served with the 78th throughout the Persian and Indian Mutiny campaigns of 1857-58. In the former he was present at the battle of Kooshab. And later he was one of the officers in charge of the small force from the 64th and 78th regiments which pushed up the Karun River from Mohumrah and took the village of Ahwaz without bloodshed while a vastly more superior enemy force looked on hopelessly from the other side of the River. 

In the Indian Mutiny he was present at all the actions in which the 78th fought, from its first taking the field in June up to and including the first relief of Lucknow of 25 September 1857. Then with the rest of the relieving force he was trapped inside the Lucknow Residency for another 55 days until Sir Colin Campbell's 'second relief' of 17 November. Afterwards he was present for the whole of the defense of the Alam Bagh position outside Lucknow, and later still at the battle of Bareilly in Rohilkhand.

Finlay was accompanied to Halifax by his wife, Mary Marcella, and by their two children. They lived, with one female servant, in a house on Tobin Street, until June 1871 when they left Halifax on Finlay's being transferred to the depot company in Aberdeen, Scotland. 

Finlay retired from the army less than two years after leaving Halifax. What he did immediately after he retired is not known; but in 1899, after the deaths of a number in the family with more immediate claims, he inherited the estate of his grandfather, and thereby became the owner of Castle Toward and Woodhay.