Colonel Scott Gehris enlisted in the Marine Corps in 1993 obtaining the rank of Corporal. Commissioned a second lieutenant in 1997 upon graduation from The Pennsylvania State University. After completing the Basic School, he was assigned as an infantry officer and reported to 3D Battalion 7th Marines in 1998. He served as a Platoon Commander, Weapons Platoon Commander and Executive Officer for India Company and deployed twice under the Unit Deployment Program. Colonel Gehris was assigned to the Basic School in 2001, where he served as an instructor, a Staff Platoon Commander, and Infantry Officer's Course Instructor. He was selected to attend the Army Infantry Captain's Career Course in Fort Benning Georgia in 2004.

In 2005, Colonel Gehris reported to 2D Battalion 4th Marines, serving as Company Commander, Operations Officer and Executive Officer. He deployed on three MEUs, with one for Operation Iraqi Freedom and two in the Pacific Theatre. In 2008, Colonel Gehris was selected to attend the Naval Command and Staff College in Newport, RI.

Colonel Gehris was assigned to Marine Corps Tactics and Operations Group in Twentynine Palms, CA, serving as an instructor and lead for the Battle Staff Training program. In 2012, he was assigned to 1st Marine Division in support of Operation Enduring Freedom as the Future Plans Officer.

Following his deployment, he was assigned as the Operations Officer and Executive Officer for 5th Marines from 2013-2014. Colonel Gehris commanded 3D Reconnaissance Battalion for two years before being selected to attend the Army War College in Carlisle, PA in 2016.

Upon completion of Top Level School, he was selected and assigned to serve as the J35 Division Chief for Joint Special Operations Command, Ft Bragg, NC from 2017-2020.

Following his joint tour, Col Gehris assumed command of Marine Corps Tactics and Operations Group from 2020-2022.

Col Gehris served as the Director of Tactical Training Exercise Control Group from May 2022 through July 2023 and was selected to be the Chief of Staff, Marine Air Ground Task Force Training Command, Marine Corps Air Ground Combat Center, Twentynine Palms in July 2023.