Sergeant Major Williamson entered recruit training January 1995 at Parris Island, South Carolina upon graduation he transferred to Fort Lee, Virginia for MOS training.

In July 1995, Private First Class Williamson was assigned the MOS of Bulk Fuel Specialist and transferred to MWSS-172 (Fuels), Camp Foster, Okinawa, Japan.  October 1995 he was promoted to lance corporal and deployed with the 31st Marine Expeditionary Unit.

In August 1996, Lance Corporal Williamson transferred to Bulk Fuel Company, 8th Engineer Support Battalion, Camp Lejeune, North Carolina.  He was meritoriously promoted to the ranks of corporal in June 1997 and sergeant in November 1998. In August 1999, Sergeant Williamson was transferred to CSSG-3, MCB Hawaii. In July 2000, Sergeant Williamson obtained a new primary MOS of Enlisted MAGTF Planner.

In February 2001, Sergeant Williamson transferred to U.S. Marine Corps Forces Pacific, Camp Smith, Hawaii.  He was promoted to staff sergeant in January 2002.  February to August 2002 he deployed to U.S. Marine Forces Central Command, Bahrain.

In May 2004, Staff Sergeant Williamson transferred to Marine Security Guard Battalion for duty as a Detachment Commander.  In July of that same year, he assumed command of MSG Detachment Manama, Bahrain.  In July 2005, he was meritoriously promoted to gunnery sergeant.  In March 2006, he activated MSG Detachment Dushanbe, Tajikistan.  In July 2007, he was assigned to a joint tour with XVIII Airborne Corps (ABC), Fort Bragg, North Carolina and deployed with Multi-National Corps-Iraq from January 2008 to April 2009.

In May 2009, he was frocked to first sergeant and transferred to 2d Assault Amphibian Battalion, Camp Lejeune, North Carolina, and served as the Company First Sergeant for H&S and Charlie Companies.  In January 2011, he deployed with Charlie Company on Unit Deployment Program (UDP) to Combat Assault Battalion, Okinawa, Japan for eight months.  In July 2012, he was transferred to 3d Radio Battalion, MCB Hawaii.

In June 2014, he was frocked to sergeant major and assumed duties as the sergeant major of Marine Tactical Electronic Warfare Training Squadron 1, Cherry Point, North Carolina.  In April 2016, he assumed the duties as the sergeant major of 2d Tank Battalion, Camp Lejeune, North Carolina.  In February 2018, he assumed the duties as the sergeant major of 22nd Marine Expeditionary Unit, Camp Lejeune, North Carolina, and deployed December 2018 to July 2019. 

In March 2020, he assumed the duties as the sergeant major of U.S. Marine Corps Forces Cyberspace Command, Fort Meade, Maryland.  The following year, U.S. Marine Corps Forces Space Command was activated adding a second MARFOR to his billet.  In  January 2023, Marine Corps Information Command was activated adding a third MARFOR to his billet. 

Sergeant Major Williamson currently serves as the U.S. Marine Corps Forces Central Command sergeant major.   

Sergeant Major Williamson’s personal decorations include Legion of Merit, Bronze Star, Meritorious Service Medal w/4 gold stars, Navy and Marine Corps Commendation Medal w/3 gold stars, and Navy Marine Corps Achievement Medal w/3 gold stars.