http://middleeast.about.com/od/usmideastpolicy/qt/me081022.htm
Ronald Reagan and the Killing of 241 U.S. Marines in Beirut in 1983

Defense Secretary Caspar Weinberger Remembers the Attack

Weinberger: Well, that’s one of my saddest memories. I was not persuasive enough to persuade the President that the Marines were there on an impossible mission. They were very lightly armed. They were not permitted to take the high ground in front of them or the flanks on either side. They had no mission except to sit at the airport, which is just like sitting in a bull’s eye. Theoretically, their presence was supposed to support the idea of disengagement and ultimate peace. I said, “They’re in a position of extraordinary danger. They have no mission. They have no capability of carrying out a mission, and they’re terribly vulnerable.” It didn’t take any gift of prophecy or anything to see how vulnerable they were.