Smith was commissioned in the United States Marine Corps as a second lieutenant in 1985 following graduation from the NROTC program at the University of North Carolina at Chapel Hill. Smith graduated from The Basic School and the Infantry Officers Course, then reported to 2nd Battalion, 1st Marines where he served as a rifle platoon commander and later as the 81 mm Mortar Platoon Commander. He then transferred to 1st Battalion, 3rd Marines, serving as Logistics Officer and Rifle Company Commander. He has served staff billets including Series and Company Commander, Marine Corps Recruit Depot San Diego; Inspector-Instructor, 4th Force Reconnaissance Company; Future Operations Planner, I Marine Expeditionary Force G-3 and G-5; and Deputy Operations Officer, 1st Marine Division. As a lieutenant colonel, Smith assumed command of 1st Force Reconnaissance Company, during which he deployed twice in support of Operation Iraqi Freedom. From 2007 to 2010, Smith was the Commanding Officer, The Basic School in Quantico, Virginia.

As a General Officer, Smith served as Commanding General, Marine Corps Air Ground Combat Center, Twentynine Palms, California; Deputy Commander, Regional Command Southwest in Helmand Province, Afghanistan; Deputy Commanding General, Marine Corps Combat Development Command, Quantico, Virginia; Director, Manpower Plans and Policy Division, Quantico, Virginia, Director, Strategy, Plans and Policy Directorate, United States Central Command, MacDill AFB, Florida, and most recently as the Senior Military Assistant to the Secretary of Defense. He assumed his duties as Deputy Commandant for Plans, Policies, and Operations from August 2019 to August 2021.