From the Marine Corps Embassy Security Guard website https://www.msgbn.usmc.mil/?pg=company/pub/about/default.htm
“The Marine Security Guards primary mission is to provide internal security services at designated U.S. Diplomatic and Consular facilities to prevent the compromise of classified information and equipment vital to the national security of the United States of America.
The secondary mission of Marine Security Guards is to provide protection for U.S. citizens and U.S. Government property located within designated U.S. Diplomatic and Consular premises during exigent circumstances, which require immediate aid or action.”
#1 The stuff
#2 The people