Alex Brown enlisted in the Marine Corps through the Delayed Entry Program in 1999 and subsequently in July 2000 attended recruit training at Marine Corps Recruit Depot Parris Island with Lima Company, Third Recruit Training Battalion.  Upon graduation, Private Brown reported to the School of Infantry, Camp Geiger, North Carolina for training as a Rifleman.
 
In November of 2000, Private Brown reported to Lima Company, 3d Battalion, 6th Marines in Camp Lejeune, North Carolina for duty as a riflemen. He deployed to Afghanistan with the 26th Marine Expeditionary Unit in the Fall of 2001 in support of Operation Swift Freedom and Enduring Freedom. Upon returning from his first deployment, Lance Corporal Brown was meritoriously promoted to Corporal and assigned to the 4th Marine Expeditionary Brigade in 2002. During the remainder of his tour with 4th MEB, Sergeant Brown deployed to Afghanistan two additional times in support of Operation Enduring Freedom and Guantanamo Bay, Cuba.  Upon returning from deployment in 2004, Sergeant Brown volunteered for the Marine Security Guard Program and reported to the Marine Security Guard School in March of 2004.  

Upon completion of Marine Security Guard School, Sergeant Brown was assigned to American Embassy Hanoi, Vietnam as the Assistant Detachment Commander.  In May 2005 Sergeant Brown was then reassigned to American Embassy Accra, Ghana as the Assistant Detachment Commander.  In May 2006 Staff Sergeant Brown was assigned to American Embassy Sofia, Bulgaria as the Assistant Detachment Commander; where he was meritoriously promoted to the rank of Staff Sergeant.  In the summer of 2007, Staff Sergeant Brown successfully completed his tour as a Marine Security Guard; and then reported to Golf Company, 2d Battalion, 8th Marines; Camp Lejeune, North Carolina as a Platoon Sergeant for a rifle platoon. 

Staff Sergeant Brown deployed with Golf Company in September of 2007 to Al Anbar, Ramadi Iraq in support of Operation Iraqi Freedom. In May 2009, Staff Sergeant Brown deployed to Helmand Province, Afghanistan in support of Operation Enduring Freedom.  After returning from Afghanistan Staff Sergeant Brown was promoted to the rank of Gunnery Sergeant. Gunnery Sergeant Brown then received orders in June 2010 to the Staff Noncommissioned Officer Academy Quantico, Virginia as a Faculty Advisor.  In July 2013, Gunnery Sergeant Brown received orders to 3d Battalion, 8th Marines; Camp Lejeune, North Carolina as the Company Gunnery Sergeant India Company.  In November 2013 Gunnery Sergeant Brown deployed as part of the SPMAGTF to Tripoli, Libya.  Prior to departing Tripoli, Libya, Gunnery Sergeant Brown participated in the evacuation and closing of the American Embassy Tripoli, Libya.  After returning from deployment in September 2014, Gunnery Sergeant Brown then received Temporary Additional Duty orders to Division Schools as the SNOIC. 

In January 2015 Gunnery Sergeant Brown was frocked to First Sergeant and received orders to Intel Company, 3d Raider Support Battalion; Marine Special Operations Command as the Company First Sergeant.  In November 2016, First Sergeant Brown reported to Headquarters Company, Headquarters Battalion, 1st Marine Division as the Company First Sergeant.  In December 2017, First Sergeant Brown deployed as part of SPMAGTF-CR-CC 18.2, as the Company First Sergeant.  Upon deactivation of SPMAGTF-CR-CC 18.2 in January of 2019, First Sergeant Brown reported back to Headquarters Battalion, 1st Marine Division. In October 2019, Sergeant Major Brown was assigned to HMLA 469, MAG 39 as the Squadron Sergeant Major. Upon the deactivation of HMLA 469 in  December 2022,  and activation of HMLA 367, Sergeant Major Brown was assigned as the HMLA  367 Squadron Sergeant Major.

Sergeant Major Brown's personal decoration and awards includes, the Meritorious Service Medal, Navy and Marine Corps Commendation Medal with Combat Distinguishing Device and three gold stars in lieu of fourth award, the Navy and Marine Corps Achievement Medal with two gold stars in lieu of third award, the Combat Action Ribbon with gold star, the Marine Corps Good Conduct Medal with one silver star in lieu of sixth award; and various other unit and service awards.