I've been watching TOS with my wife over the past year slowly as we know there are not that many episodes from this period. Every time I watch, I have my laptop and I do a bit of research on the actors and trivia about the episode.

There are many actual WWII veterans that make appearances in the show. It is interesting to note that with the show being made in the late 1960s, many of the returning veterans of the war at the time were in their 40s/50s which means they were still able to take part in shows like this.

James Doohan was a prime example ... a veteran of the front lines of the war and he was still able to build an acting career.

Walter Matthew Jefferies (August 12, 1921 – July 21, 2003) was an American aviation and mechanical artist, set designer, and writer. He is best known for his work on the original Star Trek television series, where he designed many of the sets and props, including the original Starship Enterprise, and the bridge and sick bay

After a devastating mid-air collision with a German fighter over North Africa the B-17 bomber "All American" landed safely at a remote desert airfield. It was methodically rebuilt, striped of all armament and flown by a new crew of four. Among these crew members was Matt Jefferies, who served as flight engineer and co-pilot. No longer a bomber, unarmed and incapable of defending itself, the All American was assigned to carry out special secret missions over enemy held territory.

https://memory-alpha.fandom.com/wiki/Matt_Jefferies

https://en.wikipedia.org/wiki/Matt_Jefferies

http://www.mattjefferies.com/

Gene Roddenberry was a veteran bomber pilot for the US Air Force during the Second World War

He was posted to Bellows Field, Oahu, to join the 394th Bomb Squadron, 5th Bombardment Group, of the Thirteenth Air Force, which flew the Boeing B-17 Flying Fortress.

Mark Lenard, who famously played Sarek in Star Trek, was a veteran of the Second World War, joining the US Army in 1943 and becoming a paratrooper in Europe. He rose rapidly through the enlisted ranks until he was discharged as a technical sergeant in 1946.

https://en.wikipedia.org/wiki/Mark_Lenard

https://memory-alpha.fandom.com/wiki/Mark_Lenard

My grandfather was in the army in WW2, on the Pacific front. He rarely talked about what happened to him, but he saw some horrific things (and got a Silver Star for his troubles). I've often pondered how witnessing that sort of thing changes your long-term outlook on life. After WW2, life in the US was grand, and optimism was high. For soldiers returning, how do you square that with the horrors witnessed? Star Trek seems to me the epitome of optimism. Many WW2 vets were involved in that (as you showed here), but at the same time Vietnam was getting going. I wonder how the experience of the horrors of war in their memory, and the concurrent Vietnam war were processed by them.

DeForest Kelley, who played Dr Leonard McCoy in the Original Star Trek series was a veteran of the Second World War. During the war, Kelley served in the United States Army Air Forces in a non-fighting capacity from March 1943 onward, as he, having a theatrical background at the time, was assigned to the First Motion Picture Unit, responsible for the production of propaganda, and training films.

https://memory-alpha.fandom.com/wiki/DeForest_Kelley

https://en.wikipedia.org/wiki/DeForest_Kelley

http://veterantributes.org/TributeDetail.php?recordID=1333

Remember when the US and fascists were on opposing teams?