My chemistry teacher in high school flew Navy PBYs in WWII, search and rescue of downed pilots.
After me going through the Navy, I regret never going back to ask him some questions.
I know the feeling. My 8th grade history teacher was a driver on a LST that delivered troops to shore on D-Day ETO, I learned that once in high school and thought more than once to go and A: thank him and B: ask him generally about his time in WWII. Now, he has since passed away.