This is awesome! I got really interested in Rhodesia last year, and think the guns from that time period are really interesting. That article on the A5 shotgun was rad. Check out the book Fireforce by Chris Cocks, you won't regret it. The story of the Rhodesian Light Infantry and their Fireforce tactics in the bush war is nuts!
The usual academic answer is from various archives and military academies. Pay your dues and do the necessary legwork for research.
But I personally find that answer very behind the times. The Internet may not have a central repository for military articles, but it doesn’t need to have one thanks to Google especially if you understand how to properly tune your search results.
For instance, when searching about the Rhodesian Bush war, I simply added the search term “PDF” into the query and got this as my first result:
And note that when you get your first long article, it’ll usually include a very long bibliography which you can then search for, like this:
Cox, Chris. Fireforce: One Man’s War in the Rhodesian Light Infantry. Johannesburg: 30 Degrees South, 2006.
Which you can then try to find copies of, perhaps by purchasing an ebook from Amazon:
https://www.amazon.com/Fireforce-Mans-Rhodesian-Light-Infantry/dp/0958489092
(Though in this case it seems only the paper version is available).
I would caution though that most military history accounts are terribly one-sided, so it pays to also enter search queries about the other side, and to look at sources covering the opposition.
Don’t be afraid to search in Google adding “reddit” as a search query. A lot of wars often have a few English language experts who show up in reddit, and they very often can give more details that a normal paper would not cover.
I can only second u/Dead_Rendezvous, Война / War is one hell of a good movie. It's like Chuck Norris' Missing in Action, but in really good and pseudo-realistic.
If you want a rather action-laden mini series on Chechnya, check out <em>Грозовые ворота / The Storm Gate</em>. Personally I found it better than the much-praised <em>9 ротa / 9th Company</em>.
As in books with similar style of writing and topic (but sadly not Chechnya) I can also recommend <em>Fireforce</em> by Chris Cocks, Guy Sajer's <em>The Forgotten Soldier</em>, Gustav Hasford's <em>Phantom Blooper</em> or Ahn Junghyo's <em>White Badge</em>. They all kinda have that critical, self-reflecting and pitch-black grim vibe all over them.