Eilleen, following is his military career. I didn't translate his grades, because I know nothing about this. An expert could tell you what the corresponding grade would be in the British Army. He was part of a mission in Russia and wrote a book about it.
https://www.librairiedialogues.fr/livre/3380755-en-mission-a-travers-la-russie-de-lenine--guinet-alphonse-fournier29 March 1895: Engaged as voluntary for 4 years at city hall of Chalons-sur-Saône and joined 4th regiment of Artillery
9 November 1895: 4th regiment of Artillery; Brigadier
22 September 1896: 4th regiment of Artillery; Maitre des Logis
23 March 1899: returned to army for 3 years, starting from 29 March 1899.
15 March 1901: Military School of Artillery and Genie; sous-officier
26 July 1901: re engaged for 2 years, starting from 29 March 1902
15 March 1902: 14th Batallion of Artillery on foot; sous-Lieutenant
1 April 1904: 14th Batallion of Artillery on foot; Lieutenant en second
27 September 1906: 28th Regiment of Artillery (6th Batallion); Lieutenant en second
24 June 1909: 28th Regiment of Artillery (6th Batallion); Lieutenant en premier
1 January 1911: 28th Regiment of Artillery (trainee at 116th Infantry); Lieutenant en premier
1 October 1911: 28th Regiment of Artillery (6th Batallion); Lieutenant en premier
24 April 1912: 28th Regiment of Artillery (12th Batallion); Lieutenant Commandant
24 June 1912: 28th Regiment of Artillery (12th Batallion); Capitaine
9 August 1914: Joined the troops; Capitaine
8 September 1914: Evacuated because of injuries; Capitaine
8 November 1914: Rejoined the troops; Capitaine
15 September 1917: Mission in Russia; Capitaine