Vietnam. US ADMITTED defeat. They could NOT win against the Vietcong because anybody could of been a member, and there was territorial advantage on the side of the Vietcong.
Oh, and if the US is so high and mighty, why were they fighting in Iraq for SO many years, as well as Afghanistan? Seriously, so many soldiers yet what good are they doing. Also, if the US military is so good, why are most of British soldiers deaths from friendly fire from AMERICANS?
Now, take a look at the link below,