I'm looking for army records relating to Jean Baptiste Cordier. He is listed on his son, Pierre Louis Oscar Cordier's marriage record as shown here:
I have absolutely no idea where to start with French army records.
Genealogy & Family History Stack Exchange is a question and answer site for expert genealogists and people interested in genealogy or family history. It only takes a minute to sign up.Sign up to join this community
The French military records, held at the SDH in Vincennes, have been famously difficult to access, although apparently with a recent change of leadership, things are getting better. There is one list of officers available on this page, 'Répertoire des officiers généraux', but this is, I think, only for the higher ranks, and your man is not found there.
At any rate, this almost would certainly require a visit there (by yourself or another researcher). However, one can often turn up references in various official documents/army lists either at http://gallica.bnf.fr/ or https://books.google.com/ . The ideal search is to use a phrase search with the name in last name, first name order, e.g. "Cordier Jean Baptiste Alexandre", also trying initials and abbreviations (Bte or Bapt. for Baptiste, for example)
No hits on Gallica, but on Google Books there are a couple references (using the full name search as above):
Bulletin des lois de la République Française, Volume 27: Lists of military pensioners, 14 February 1845
This shows him as born 16 Oct 1795, Toulouse. His rank is listed as Lieutenant a la compagnie de gendarmarie de la Vendee.
There are also two hits from Annuaire de l'etat militaire de France - one in 1842, giving his location as Bourbon-Vend (Bourbon-Vendee, another name for La Roche-sur-Yon), one in 1845 which has 'Aux Herbiers' (Les Herbiers, perhaps, also in Vendee?).
Lastly, because he was just old enough to be in the army in 1815, I thought to check him in the Ste Helene Medal database: http://www.stehelene.org/php/accueil.php?lang=en These were given to soldiers who had fought for Napoleon, and were still living in 1857.
His entry shows him as living in Hede when he received the medal, his regiment is listed as 'gendarmerie de la garde', and the period of service is listed as 29 09 1813-1815. (He served after this, but this was the period of his service which made him eligible for this medal, I suppose).