Ripley was given a grave "hold and die" order during the 1972 Easter Offensive to blow up a pair enemy bridges by crawling under them and rigging up to 500 pounds worth of bomb materials to bring them down. He did this in part by hand crawling, monkey bar style, under the bridges while carrying the heavy bomb equipment.
His brave feat helped stop 200 tanks from rolling in South Vietnam and miraculously, he lived to tell the tale.
Ripley recounted his mission for the U.S. Naval Institute in the clip below. God bless you, Col. Ripley! Hoorah!