Sergeant Major Michael B. Allen enlisted in the U.S. Marine Corps and reported to Marine Corps Recruit Depot, Parris Island, SC, in July 2002.
In October 2002, Private Allen was meritoriously promoted to Private First Class. Subsequently, in November 2002, Private First Class Allen reported to Camp Johnson, North Carolina, for the Basic Warehouseman School. Upon graduation, he received the Military Occupational Specialty (MOS) 3051, Warehouse Clerk, and was meritoriously promoted to Lance Corporal.
In January 2003, Lance Corporal Allen reported to 2d Supply Battalion, Camp Lejeune, NC, where he was selected for the Fleet Assistance Program and subsequently served as a Military Policeman with Headquarters and Support Battalion, Provost Marshal's Office, Camp Lejeune, NC. In February 2005, he was promoted to Corporal.
Corporal Allen was promoted to Sergeant in June 2006. In August 2006, he attended Military Police School, earning the MOS 5811, Military Policeman, and subsequently reported to the Provost Marshal's Office, Camp Butler, Okinawa, Japan, where he served as the Platoon Sergeant and Watch Commander for Military Police Districts East and North. In September 2007, Sergeant Allen reported to the Provost Marshal's Office, Camp Lejeune, NC, serving as a Patrol Supervisor and Training Non-Commissioned Officer (NCO). In July 2009, Sergeant Allen reported to Drill Instructor School, Parris Island, SC. Upon graduation, he was assigned to Delta Company, 1st Recruit Training Battalion, where he served as a Drill Instructor and Senior Drill Instructor. He was promoted to Staff Sergeant in November 2010.
In September 2012, Staff Sergeant Allen reported to the Provost Marshal's Office, Camp Pendleton, CA, where he served as a Platoon Sergeant, Watch Commander, and Company Gunnery Sergeant. During this assignment, he deployed in support of the Marine Corps Training Mission in the United Arab Emirates. In November 2015, he was promoted to Gunnery Sergeant and served as the Company First Sergeant for the Provost Marshal's Office, Camp Pendleton, CA.
In August 2016, Gunnery Sergeant Allen reported to the University of California, Los Angeles (UCLA), Los Angeles, CA, where he served as the Assistant Marine Officer Instructor for the Naval Reserve Officers Training Corps (NROTC).
In July 2019, Gunnery Sergeant Allen reported to the Provost Marshal's Office, Headquarters and Headquarters Squadron, Marine Corps Air Station Miramar, San Diego, CA. During his tour, he served as a Watch Commander and was selected for promotion to First Sergeant.
In January 2020, First Sergeant Allen reported to 3d Assault Amphibian Battalion, 1st Marine Division, Camp Pendleton, CA, where he served as the Company Senior Enlisted Leader for Company A. He deployed to the Western Pacific in support of the Unit Deployment Program. In December 2021, First Sergeant Allen reported to 1st Intelligence Battalion, I Marine Information Group, Camp Pendleton, CA, where he served as the Company Senior Enlisted Leader for Headquarters Company. He was selected for Sergeant Major during this tour.
In January 2024, Sergeant Major Allen reported to Combat Logistics Battalion 7, Twentynine Palms, CA, where he served as the Command Senior Enlisted Leader. In November 2025, Sergeant Major Allen reported to HMLA-367, Camp Pendleton, CA, assuming the responsibilities of Command Senior Enlisted Leader.
Sergeant Major Allen's personal awards include the Meritorious Service Medal, the Navy and Marine Corps Commendation Medal (3rd award), and the Navy and Marine Corps Achievement Medal (3rd award).