i have just a single recommendation i hope you find valuable, though it's not about rpgs or even video games at all (although it does have a peripheral connection to the work of doug engelbart, which is how i know about it).

the new games book is a 70s-era book that arose from the countercultural movement started by stewart brand, and specifically from his publishing team that created the whole earth catalog. its philosophy is explicitly and emphatically one of cooperation and collaboration, though not at the expense of competitive games.

one of the original games was called slaughter and (as documented in the book) was intended as an an anti-vietnam war protest . stewart took these ideas to create "play-in," though eventually they developed into an entire movement more focused on the games than politics.

one other thing i'll sneak in at the end of post (sorry mods!) that you probably already know about it is the strong anti-nuclear proliferation themes present in the works of hideo kojima, especially in the metal gear series.

Shannon Appelcline's Designers & Dragons series is a good overview of RPG publishers and tracks the evolutions and trends and constant economic failures of the companies themselves. Not exactly what you're asking for but you can see the evolution of RPG's through the companies that develop. While not a historian he did lots of research and interviews.

I hope that you are aware of Playing at the World by Jon Peterson. Not only is it a biography of the original Dungeons & Dragons, it also touches on the development of the board game and roleplaying mediums. This includes the use of games in a military context, including those at RAND Corporation during the Cold War. It is exhaustively researched, an extremely elaborate tome with incredible citations.

Unfortunately, it is currently no longer in print. An ebook version was offered a few years ago so that would be findable, but he is working on a revised edition. No idea when that will be available.

For a general history of board games and the American industry, check out Tristan Donovan's It's All a Game: A Short History of Board Games from a few years ago. It's more of a popular history, but he is good about citations and did legitimate research in the papers of the Strong Museum in Rochester (which is the leading institution for games of all types currently).

In video games, my friend Alex Smith's first volume of three They Create Worlds: The Story of the People and Companies That Shaped the Video Game Industry, Vol. I: 1971-1982 is the best contextual look at early video games available. Bias included, but he's diligent and puts things into context in a way that basically no other author has done. Video games is my field so if you need more info I can point you to more resources. I even have a dedicated booklist just on this subject.

There are also resources out there for the history of coin-operated games in the 20th century, such as Dick Beuschel's books Arcade 1 and Encyclopedia of Pinball series. The coin-op world has some interesting things to think about as far as the context of militarism in society, not just in the US but elsewhere. That's not really been tackled by scholars though.

If you're still looking for more specific resources, I can dig those up for you! I find your subject really interesting and I hope this list can help you in that work; I hope to see it in the future!

I had a number of suggestions to you that I am just now getting to record with the end of the American Thanksgiving holiday. My own interests (both as an amateur researcher and historian) tend towards hobby wargaming (specifically board wargaming in the American Avalon Hill-SPI tradition) which sits somewhat between professional wargaming and roleplaying.

Jon Peterson, Playing at the World (2012) is the closest thing to a social history of wargaming and roleplaying that has been published, with the caveat that this coverage is focused quite tightly on the circumstances in the 1960s-70s that led to the birth of Dungeons & Dragons. The coverage of hobby wargaming is quite good and to my mind renders Peter Perla, The Art of Wargaming (1990, rev. ed. 2012) and Thomas B. Allen, War Games (1987) superfluous for hobbies. (On the other hand, Peterson makes some pretty contestable conclusions about professional wargaming, so Perla and Allen continue to have value there but have been superseded somewhat.) Peterson continues this story in The Elusive Shift (2020) which is really about the initial reception of Dungeons & Dragons. Game Wizards (2021) gets perhaps a bit more into the history of a particular game company, of which Shannon Appelcline has provided quite a few in his series Designers & Dragons (2014ish). Peterson is somewhat distinct from other authors purporting to tell you the true story of D&D, whether Gygax or Arneson was the true creator, etc. because he strongly privileges written sources.

For wargaming I have mentioned Perla and Allen who wrote at what we can now periodize as the end of the hobby and professional wargaming boom of the 1960s-80s. More recently there's Matt Caffrey, On Wargaming (2019, free U.S. government publication) which emphasizes the professional side; however, there was a strong relation between the two as Caffrey's own career shows: his professional career in the Air Force was focused on wargaming, but he also coauthored The Gulf War Fact Book (1991) with hobby wargame designer Frank Chadwick (a publication that played a key role in that company's history).

A recent roundup is the collection of papers published as Pat Harrigan & Matt Kirschenbaum, eds., Zones of Control (2016). The list of contributors is basically a who's who of contemporary wargame design, mostly for the hobby market but with some from the professional military/analysis community.

I don't mean to misread or dictate your project, but it seems like there's a considerable intersection between your interests and those of Phil Sabin, with whom I presume you've crossed paths. Sabin was one of the founders of the Wargaming Network at Kings College London, maybe the dean of academic wargaming in the UK as well as the designer of several hobby games, and his most notable work on wargaming is Simulating War (2012), which fits in the tradition of "how-tos" and includes a number of games designed by KCL students. But Sabin's first book was The Third World War Scare in Britain (1986) which discussed public concern about a war against the Soviet Union in the late 1970s and early 1980s. I think Sabin is retired in South America now. Sabin's book helped me understand better the context of hobby wargames on WWIII set during that period.

I'd also note that within the hobby wargaming space there has been a considerable resurgence of interest in the topic of WWIII during the 1970s-80s, which is now alternate history. This had been one of the most popular topics from the mid-1970s to almost exactly 1990. Since about 2016 the majority of hobby wargame publishers have published titles on this topic, in some cases publishing new editions of now-classic games from that era (for which nearly all the original designers are still available) and in others completely new titles. You can also see this resurgence in miniatures wargaming, computer wargaming, and to a lesser extent roleplaying. Why this is happening is a topic of considerable interest within the hobby; I have my theories.

I can also point you to a few works, some in English and some in German, on the intersection of Cold War reality and wargaming at the Fulda Gap, but this may be too focused for you.