Joshua A. MacMillan was born and raised in Royal Oak, Michigan. In 2007, he attended recruit training in Lima Company, 3rd Recruit Training Battalion, Marine Corps Recruit Depot Parris Island, South Carolina. He then reported to the School of Infantry at Camp Geiger, North Carolina to attend the school of Infantry and upon graduation, received the primary military occupational specialty of Infantry rifleman 0311.
In December of 2007, Private First Class MacMillan reported to Washington, DC Marine Barracks Washington where he served as a rifleman, but also served as honor guard, performing funerals and Department of Defense ceremonies in the national capital region. While there, Private First Class MacMillan attended Infantry Small Unit Leaders Course and was promoted to Lance Corporal.
In December of 2009, Lance Corporal MacMillan reported to 3d Battalion, 8th Marines, Kilo Company as a rifleman and as a machine gunner. During this time, Lance Corporal MacMillan attended the Martial Arts Instructor Course. Lance Corporal MacMillan deployed twice with V38, once in 2010 to Sangin, Afghanistan where he was meritoriously promoted to Corporal and reenlisted for four years, and another in 2012 to Garmshir, Afghanistan where he was meritoriously promoted to Sergeant.
In July of 2013, Sergeant MacMillan reported to Chemical Biological Incident Response Force (CBIRF) in Indian Head, Maryland where he served as a section leader and a “hot zone controller”, the downrange commander in a chemical or biologically contaminated area. Sergeant MacMillan was meritoriously promoted to Staff Sergeant on 2 April, 2016. After his promotion, Staff Sergeant MacMillan reenlisted again and held the billet as a Platoon Sergeant. While at CBIRF, Staff Sergeant MacMillan attended the Martial Arts Instructor Trainer Course, Career Course, and Infantry Unit Leaders Course prior to executing orders back to the Fleet Marine Force.
In July of 2016, Staff Sergeant MacMillan reported to 3d Battalion, 6th Marines, Kilo Company and served as a Platoon Sergeant. In 2017, 3d Battalion, 6th Marines deployed on the 24th MEU, and his Platoon was chosen to forward deploy in support of Operation Inherent Resolve in Syria. Staff Sergeant MacMillan was promoted to Gunnery Sergeant on 1 December, 2018 and deployed to Okinawa, Japan on the Unit Deployment Program (UDP) while serving as Combined Anti-Armor Team Platoon Sergeant in Weapons Company. Upon his return from the UDP, Gunnery Sergeant MacMillan was selected to receive the Jerry Coleman Act of Valor award, a service level award for volunteerism and leadership, presented in Washington D.C by the Sergeant Major of the Marine Corps. Gunnery Sergeant MacMillan served as the Assistant Operations Chief for Weapons Company for the remainder of his time at 3d Battalion, 6th Marines until receiving and executing orders in December 2019.
In January of 2020, Gunnery Sergeant MacMillan reported to Headquarters and Service Battalion, MCB Quantico where he served as the Combat Development Company and Headquarters Company Gunnery Sergeant and acting 1stSgt. In February of 2022, he was frocked to the rank of First Sergeant and executed orders to Dayton, Ohio to serve as the Inspector-Instructor First Sergeant for Military Police Company “C”. In June of 2025 he was frocked to the rank of Sergeant Major and executed orders to Milwaukee, Wisconsin to serve as the RS Sergeant Major.
Sergeant Major MacMillan’s personal decorations include the Meritorious Service Medal, Navy and Marine Corps Commendation Medal (gold stars in lieu of third award), the Navy and Marine Corps Achievement Medal with Combat “V” (gold star in lieu of second award), the Combat Action Ribbon, and the Military Outstanding Volunteer Service Medal.
Sergeant Major MacMillan is married to Rebecca MacMillan and has four children, Dominic, Brooklyn, Carter, and Mackenzie. They live in Kewaskum, WI.