Bert,
You found an implication, “your post implies we should know all, even secret stuff,” that I did not imply.
I have spent many years as an Army intelligence officer and afterwards being involved with declassification. I will state that I do BELIEVE that 95% of all military classified has a expiration date after which it can and should be declassified.
Sometimes events are kept secret because they would be embarrassing if known. Someone in Gulf War 1 told me about some stupid fatal actions by our troops that never made it into the news.