Sergeant Major Forrest C. Allen was born in Raleigh, NC, on 21 November 1982. He joined the Marine Corps in April 2003, reporting to MCRD Parris Island.
After boot camp, Private First Class (PFC) Allen attended Marine Combat Training and proceeded to 29 Palms, CA, where he excelled in the Data Network Systems Specialist Course and the follow-on Tactical Data Networking course, earning a promotion to Lance Corporal (LCpl).
In February 2004, LCpl Allen reported to Communications Company, 3d Force Service Support Group. While there, he supported multiple annual training deployments, rotations with the 31 MEU Service Support Group, and humanitarian missions. During this period, he was promoted to Corporal in Japan and Sergeant (Sgt) in Guam.
In April 2007, Sgt Allen began a successful tour of Drill Instructor Duty at MCRD Parris Island. He served with 3d Bn Co K and later transferred to the MCRD Swim Tank as a Marine Corps Instructor of Water Survival. During this time, he was promoted to Staff Sergeant (SSgt). In January 2010, SSgt Allen returned to 3d Bn as a Senior Drill Instructor with Co M.
SSgt Allen was transferred to Transportation and Support Company, Combat Logistics Bn 8, in May 2010. He served as the Company Gunnery Sergeant and deployed to Afghanistan in January 2011. Following this deployment, he was reassigned as the Communications Chief for CLR 2 aboard Camp Lejeune.
In November 2012, SSgt Allen reported to Expeditionary Warfare School, Quantico, VA, as the Communications Chief and Senior Enlisted Advisor. Following his selection and promotion to Gunnery Sergeant (GySgt), he moved to the Command and Staff College, continuing to run the Enlisted Education Program. GySgt Allen also served multiple cycles as a Sergeant Instructor and Platoon Sergeant at Officer Candidate's School.
GySgt Allen transferred to 1st Marine Division in August 2016 as the Division Network Chief. Upon selection for promotion, 1stSgt Allen was transferred to Co E, 2d Battalion 5th Marines, and immediately deployed to Okinawa, Japan, as part of the Battalion Landing Team to the 31st MEU. He executed a subsequent deployment to the United States Embassy in Baghdad, Iraq, in March 2020. Upon his return, he served as a 1stSgt at the School of Infantry East.
Sergeant Major Allen was promoted to his current rank in December 2022 and transferred to 2d Combat Engineer Battalion, immediately deploying to Europe as part of Marine Rotational Forces Europe 23.1. In November 2025, he was assigned to 2d Marine Regiment, where he currently serves.