U.S. Marines and Navy Corpsmen line up to load casualties aboard H 34 Marine helicopter at Con Thien, just below the demilitarized zone, in Vietnam on May 17, 1967 during the Vietnam War. The call has echoed through history, "The Marines have landed," and it usually heralds a new course for a war. Sometimes comes a quick, overpowering victory, sometimes a savage morass. (AP Photo)