There was a lot of people asking questions about the previous war and current wars, including the Vietnam War which was happening at the time.

I think the combination of veterans of Second World War, Korean War and the terrible experiences they had meant that they were more than willing to ask pertinent questions about any war.

For example ‘A Private Little War’, episode 19 from season 2 of TOS which aired in February 1968 is seen as an allegory of the Vietnam War … the powerful federation and the Klingon Empire trying to manipulate and affect control over a weak neutral planet, which then leads to conflict on the once peaceful population.

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

It’s really striking when you realize that the episode aired in February 1968, a month after the Battle of Khe Sanh and the start of The Tet Offensive which all happened in January 1968. Major battles and events were happening in Vietnam and the writers and producers air an episode on Star Trek asking and displaying why two great powers (Soviet Union and the United States) are fighting or starting conflicts in once peaceful places. The episode didn’t provide any answers but it certainly asked a lot of important questions for everyone to think about.

There are a few other examples like this from the TOS series but this episode was one of the most obvious ones.

A SIDE NOTE: … I took two trips to Thailand, once in 1999 and another in 2015. We did a lot of budget travelling when we were younger and stronger in 1999 which meant we stayed in a few shady places, including one little bungalow rental place near Trang in the sound of Thailand. We met a middle aged man who was about 50 at the time but built like a muscular 20 year old and as lean. He was a veteran of the Battle of Khe Sanh and he’s the one that explained to me that the Americans regularly used any Southeast Asian looking person to fight as a Vietnamese soldier. The old guy told us in his broken English how he watched RPGs fly onto their base and how he stayed up for days avoiding these rockets to stay alive.

During that visit to his place in Thailand in 1999 we came back to his place very late one night at around 2am, I can still see him standing at the gate to his place asking forcefully who was there. It was hot and he stood there shirtless shimming in a layer of light sweat over his tough frame and holding a machete ready to fight. Once he knew it was us, he quickly turned into his nice friendly self and helped us into his property again. The man was scary but also one of the kindest people we met on that trip.