MARINE MISSION U.S. Army Gen. Martin E. Dempsey, chairman of the Joint Chiefs of Staff, meets with U.S. Marines in Hanoi, Vietnam, Aug. 14, 2014. The primary mission of the Marine Security Guard is to provide internal security at designated U.S. facilities to prevent the compromise of classified material vital to the national security. SHARE: Download: Full Size (0.06 MB) Credit: VIRIN: 542623-D-NJJ21-305.jpg Photo Gallery