There are two points there.
The first point is that the United States had 600,000 troops in Vietnam and was beaten. They're not going to put an army on the mainland of Asia ever again. We might have a war with China, and if they side absolutely with Japan, that's highly likely.
Korea is out of the act compared to today's circumstances. We had people there, as you did, and a lot of them suffered severe casualties, but it was a different war, a different time, in different circumstances. Modern technology and modern weapons have made the Korean experience irrelevant to today.
The second and, I suppose, more substantive point is that article 21.3 quite specifically gives protections to the individuals you're concerned for, and I would also be concerned for. The military personnel or nationals of state parties are individual men or women. It's not just a state party or the army or whatever, it is the individuals who make it up that have the protection under those words.