Marine Security Guard A Marine Security Guard , also known as a Marine Embassy Guard is a member of the Marine Corps Embassy Security Group , ( formerly Marine Security Guard Battalion ) , a battalion - sized organization of U . S . Marines whose detachments provide security at American embassies , American consulates and other official United States Government offices such as the U . S . Interests Section in Havana , Cuba , or the United States Mission to NATO in Brussels , Belgium . History . The U . S . Marine Corps has a long history of cooperation with the U . S . State Department , going back to the early days of the country . From the raising of the American flag at Derna , Tripoli and the secret mission of Archibald H . Gillespie in California , to the Boxer Rebellion at Peking , Marines have served many times on special missions as courier s , guards for embassies and legations , and to protect American citizens in unsettled areas . The formal and permanent use of Marines as security guards began with the Foreign Service Act of 1946 , which authorized the Secretary of Navy to , upon the request of the Secretary of State , assign Marines to serve as custodians under the supervision of the senior diplomatic officer at a diplomatic post . The first joint Memorandum of Agreement was signed on 15 December 1948 regarding the provisions of assigning Marines overseas . Trained at the Foreign Service Institute , the first Marines arrived at Tangier and Bangkok in early 1949 . The Marine Corps assumed the primary training responsibility in November 1954 . The authority granted in the Foreign Service Act of 1946 has since been replaced by and the most recent Memorandum of Agreement was signed in August 2008 . In response to the 2012 Benghazi attack , Congress ordered a near doubling of Marine Security Guards in the midst of a post - war drawdown in overall USMC numbers . The USMC has responded by redeploying one company from 1st Battalion 1st Marines while additional guards are trained . Responsibilities . The primary mission of the MSG is to provide security , particularly the protection of classified information and equipment vital to the national security of the United States at American diplomatic posts . This is accomplished under the guidance and operational control of a civilian federal agent of the Diplomatic Security Service , known as the Regional Security Officer ( RSO ) who is the senior U . S . law enforcement representative and security attaché at U . S . diplomatic posts around the world . In addition , MSGs provide security for visiting American dignitaries and frequently assist the RSO in supervising host country and / or locally employed security forces which provide additional security for the exterior of embassies . The MSGs fall under operational control of the RSO and are administratively controlled by the Marine Corps Embassy Security Group . 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 . MSGs focus on the interior security of a diplomatic post ' s building ( s ) . In only the most extreme emergency situations are they authorized duties exterior to the building ( s ) or to provide special protection to the senior diplomatic officer off of the diplomatic compound . MSGs carry a certain level of diplomatic immunity in the performance of their official duties . Organization . The Marine Security Guards number approximately 1000 Marines at 150 posts ( also known as " detachments " ) , organized into nine regional MSG commands and located in over 135 countries in 18 time zones , as well as its headquarters at Marine Corps Base Quantico . Headquarters Company , along with MSG School , is composed of approximately 100 Marines providing administrative , logistical , legal , training and education support . The remaining nine companies are commanded by a lieutenant colonel , and typically entail a number of detachments in several countries . The companies are as follows : Each Detachment is commanded by a Staff Non - Commissioned Officer , being one of the few instances where an enlisted Marine may hold the title of " commander " . Generally between the ranks of Staff Sergeant and Master Gunnery Sergeant , Marine Detachment Commanders serve two tours which generally last 18 months each . Unlike their subordinates , however , Detachment Commanders may be married . The minimum detachment size is five MSGs ( Marine Security Guards ) and a single detachment commander . This allows for posts to be manned at all times while allowing each of the Marines to conduct other routine training , internal management of the detachment and have some time off . A Marine Security Guard usually serves three 12 - month tours of duty . Marine Security Guard " watch standers " are enlisted Marines from the rank of Private First Class to Staff Sergeant . Duty . After every 24 months as a Marine Security Guard or Regional officer with the Marine Corps Embassy Security Group , a Marine is entitled to the Marine Corps Security Guard Ribbon or a subsequent service star . Marines of any Military Occupational Specialty may volunteer for a three - year tour of duty ; however , non - Staff NCOs with dependant s are not eligible , as well as Marines with potentially offensive tattoo s , legal or security restrictions , non - United States citizenship , dual citizenship , significant financial indiscretions , and any other restriction that would prevent a top secret clearance . Before being assigned to a Foreign Service post , a Marine accepted into the MSG program must successfully complete a training program located at the Marine Corps Embassy Security Group ( MCESG ) which is located at Marine Corps Base Quantico , VA . Marine Security Guard duty is one of a few special duty assignments available to qualified Marines . Marine Security Guard duty can be dangerous ; there have been instances where Marines have been killed during this duty ( most recently , Cpl Steve Crowley in 1979 , Cpl Robert V . McMaugh in 1983 and Sgt Jesse Aliganga in 1998 ) .