Lieutenant Colonel Barnhart Jr was commissioned upon graduation from the Officer Candidate Course (OCC) in Dec 1999. After completing the Basic Officer and Infantry Officer Courses, he was assigned to 1st Battalion, 2nd Marines and served as a Rifle Platoon Commander and Weapons Platoon Commander during deployments to Okinawa, Japan (2001) and Guantanamo Bay, Cuba (2002), and served the Weapons Company Executive Officer during Operation Iraqi Freedom I (2003).
In October 2003, Lieutenant Colonel Barnhart Jr. was selected to the supplementary MOS program. He reported to the Production and Analysis Company, 2d Intelligence Battalion for intelligence officer training. He subsequently graduated the MAGTF Intelligence Officer Course (MIOC) in Dam neck, VA in March 2004.
In April 2004, Lieutenant Colonel Barnhart Jr. reported to 3d Marine Regiment and served as the Assistant Regimental Intelligence Officer until October 2004. In November 2004, he reported to Special Operations Command, Pacific (SOCPAC) and was subsequently assigned as the Executive Officer/Support Center OIC, JSOTF-Philippines (FWD).
In April 2005, he reported to 1st Battalion, 3d Marines where he served as the intelligence officer and deployed in support of Operation Enduring Freedom-Afghanistan in January 2006. In June 2006, Lieutenant Colonel Barnhart Jr. graduated Expeditionary Warfare School (AY 07/07) and was subsequently assigned to Officer Candidate School (OCS) where he served as Student Platoon Commander, Company A (PLC Junior).
In September 2007, he reported to 1st Battalion, 2nd Marines and assumed command of Weapons Company. He commanded the Mobile Assault Company during a combat deployment to Iraq in 2008. Upon return from deployment in 2009, he assumed the duties as Operations Officer and deployed in support of Operation Enduring Freedom-Afghanistan in February 2010.
In January 2011, he reported to the Tactical Training and Exercise Control Group (TTECG), Twenty-nine Palms, CA where he served as the Deputy Officer-in-Charge and Corridor/Maneuver Coyote for Infantry Battalion Team East. During his time at TTECG Lieutenant Colonel Barnhart Jr. completed the Marine Corps Command Staff Distance Education Course as a Distinguished Graduate.
In July 2014, Lieutenant Colonel Barnhart Jr. graduated from the School of Advanced Warfighting (AY 13/14). He then reported to 3d Marine Expeditionary Brigade where he served as the plans and exercise officer. In July 2017, he assumed duties as the Regimental Operations Officer for 23d Marine Regiment, San Bruno, CA.
In June 2018, he received orders to serve as the Commanding Officer of 1st Battalion, 7th Marines in 29 Palms, CA.
His personal awards include the Bronze Star, Meritorious Service Medal (with Gold Star in lieu of second award), Navy Commendation Medal (with Combat Distinguishing Device w/ 3 Gold Stars in lieu of fourth award), Navy Achievement Medal, Army Achievement Medal, and the Combat Action Ribbon (Gold Star in lieu of second award).
He holds a BS in Environment Science from the University of Idaho and MA in Operation Studies from Marine Corps University.