These two playlists by Ryan McBeth (a SWE, former anti-tank infantryman) are very interesting:
Military equipment, tactics and strategy: https://www.youtube.com/watch?v=r2s0Szx-kVs&list=PLt670_P7pO...
40 short Q&A videos about Ukraine : https://www.youtube.com/watch?v=M8mJ7hG9xM8&list=PLt670_P7pO...
* The Chieftain: https://www.youtube.com/c/TheChieftainsHatch . He has a series on the development of Armored doctrine for various nations prior to WW2 which is a very interesting dive into what military doctrine is and how it is formed.
* Battle Order https://www.youtube.com/c/BattleOrder covers how troops are organized and divided into squads/platoons/companies/battalions/etc in various countries and at various times.
* If you are interested in World War 2, the World War 2 in real time series on YouTube is also fascinating: https://www.youtube.com/c/WorldWarTwo .
* For getting the perspective of national security experts dealing with current events, I would take a look at https://warontherocks.com , which has a mix of articles and associated podcasts. The war on the rocks podcast has been doing weekly updates on the state of the war in Ukraine with Michael Kofman, director for the Russia Studies Program at CNA. I've found those very informative.
* Arms Control Wonk (https://www.armscontrolwonk.com/ ) the blog and podcast are interesting for looking at the military from the point of view of strategic stability.
* https://acoup.blog/ is run by a professor of military history. He covers a variety of topics; he does several series analyzing the historical realism of video games and movies for example. But he also discusses some of the fundamentals of military theory, and tends to focus a lot on what the popular imagination gets right and wrong about the military and warfare throughout the ages.
* There are think tanks like the RAND corporation, CSIS, and CNA that publish papers on a variety of topics in military theory and policy. With a little effort, a lot of them are fairly readable to the layman
* For the deepest dive, the US Army field manuals are publicly available if you search around. Skimming through them gave me a much better understanding of how an officer goes about planning an attack, preparing a defense, setting up an ambush, etc.
(It's been a while since I’ve spent time with this; one which I remember finding interesting was Breaking the Phalanx: A New Design for Land Power in the 21st Century. [0])
[0] https://www.goodreads.com/book/show/1597250.Breaking_the_Pha...
I found him through the youtube algo, used to be a gaming youtuber but seems to have a day job in defense and started talking about the Ukrainian war. Hour long data dense powerpoints about what's going on over there. Easily my favorite source.
https://www.youtube.com/channel/UCC3ehuUksTyQ7bbjGntmx3Q/vid...
While the technologies he describes are a bit dated, his presentation is very comprehensive. Only problem is that many of his works are out of print.