I had a good idea after I read Panda's blog about his (really good) airsoft event idea. So after looking through some untold battles and conflicts, I came across the 1968 invasion of Czechoslovakia. I'll give a small summery of this conflict.

August 1968. Soviet Russia invaded the Czechoslovak Socialist Republic in order to stop Alexander Dubček from continuing the Prague Spring
In the end, Russia invaded Czechoslovakia as the world turned it's head to the terrors in Vietnam....