I didn't vote for Clinton or Barry, so I'm not sure why you're bringing them up. They have nothing to do with Trump and his cowardice. That's called deflection.
As for Biden, he didn't live through two world wars; he was born in 1942, about a year after the U.S. entered World War II. He was not old enough to serve in Korea. The only war that you mentioned that he was old enough to serve in was the Vietnam War.