Lieutenant Colonel John Mullen, a native of Spokane, Washington, began his career in the United States Marine Corps in January of 2006 after graduating from Washington State University with a Bachelor of Science in Electrical Engineering.

Following his completion of the Basic School and Infantry Officer's Course, Second Lieutenant Mullen was assigned to 3rd Battalion, 5th Marines, where he served as a Rifle Platoon Commander and deployed in support of Operation Iraqi Freedom. Upon his return from Iraq in May 2008, 1stLt Mullen assumed the duties of Company Executive Officer and completed another deployment with the 31st Marine Expeditionary Unit.

In 2009, Lt Mullen was selected for Marine Forces Special Operations Command (MARSOC) and served as the 3d Marine Special Operations Battalion (MSOB) Training Cell OIC until the beginning of the Individual Training Course (ITC). After completing ITC in 2010, he was assigned to 3d MSOB as a Company Executive Officer. In May 2011, he was appointed as Team Commander for Marine Special Operations Team (MSOT) 8333. In this role, Captain Mullen deployed twice in support of Operation Enduring Freedom – Philippines.

After graduating the Maneuver Captains Career Course 2014, Captain Mullen was assigned to serve as the Raids OIC for the II MEF Expeditionary Operations Training Group.  In 2015 He was assigned as a Special Operations Training Cadre OIC for the Marine Raider Training Center. In 2016, Major Mullen assumed the role of Regional Engagement Officer in the MARSOC G-35.

In 2018, Maj Mullen took command of Marine Special Operations Company – G, 2d Marine Raider Battalion, deploying in support of Operation Inherent Resolve in 2019.

Following his graduation from the United States Marine Corps Command and Staff College in 2021, Maj Mullen was assigned to PP&O, where he ultimately served as the Future Force Management Section Head.

In June 2024, LtCol Mullen assumed the duties of 4th Reconnaissance Battalion Inspector-Instructor.