Colonel Wittnam was commissioned in April 1995 after serving as an Infantryman in 1st Battalion, 7th Marines. After completing The Basic School and the Infantry Officers Course he was assigned to Lima Company, 3rd Battalion, 2nd Marines and served as a Rifle Platoon Commander, Weapons Platoon Commander and Company Executive Officer. During this tour he deployed to Okinawa, Japan as part of the Unit Deployment Program (UDP) and to the Mediterranean on the 26th Marine Expeditionary Unit.
He reported to 3rd Reconnaissance Battalion in Okinawa, Japan in November 1998 where he served as Reconnaissance Platoon, Headquarters Company Commander and Battalion Operations Officer and deployed as the Force Reconnaissance Platoon for the 31st Marine Expeditionary Unit.
In January 2002, Colonel Wittnam reported to Fort Benning, Georgia and attended the U.S. Army’s Infantry Captains Career Course and was a Distinguished Graduate.
In June 2002, he assumed duties as the Company Commander, Charlie Company, 1st Battalion, 2nd Marines. He commanded the Company during Operation Iraqi Freedom in March 2003. In 2004, he assumed the duties of the Assistant Operations Officer at 2nd Marine Regiment before being selected to lead Small Craft Company, a Riverine unit, back to Iraq in 2004 and 2005. During this tour Small Craft Company was attached to 3rd Light Armored Reconnaissance Battalion during Operation Al Fajr, the 2nd Battalion of Fallujah.
In June 2005, he reported to Tactical Training and Exercise Control Group (TTECG) where he served as the Maneuver Coyote, Urban Warfare Instructor and was assigned as the Officer In Charge of the Combined Arms Training Program.
In July 2008, Colonel Wittnam reported to Naval Command and Staff College in Newport, Rhode Island and earned a Master of Arts Degree in Strategy and National Defense Planning.
In June 2009, he was assigned as an Operational Planner at United States Southern Command in Miami, Florida. During this tour he served as the lead contingency planner following the Haiti Earthquake in January 2010 and was later assigned as the Aide de Camp to the Combatant Commander.
In June 2011, Colonel Wittnam was assigned as the Future Operation Officer at 5th Marine Regiment during a yearlong deployment to Helmand Province, Afghanistan. During this deployment the Regiment transitioned responsibility of Southern Helmand Province from Marine forces to Afghan Security Forces. Upon returning from this deployment he was assigned as the 5th Marines Operations Officer.
Colonel Wittnam assumed command of 3rd Battalion, 7th Marines in February 2013 and deployed back to Northern Helmand and was tasked with transitioning four provinces from U.S. Marine control back into the hands of the Afghanistan Security Forces.
In June 2014, he was assigned as Branch Head of the Instructor Group at the Marine Corps Tactics and Operations Group (MCTOG). He was responsible for transitioning the curriculum to outcomes based learning and was the lead evaluator for Regimental Headquarters Command and Control during Exercise Spartan Advance and the Large Scale Exercise.
In June 2016, Colonel Wittnam reported to the Eisenhower School at the National Defense University and earned a Masters of Arts Degree in Strategy and Resourcing.
In June 2017, Colonel Wittnam was assigned to Headquarters Marine Corps, Plans, Policy and Operations where he served as the Ground Combat Element Advocate. In November, 2019 Colonel Wittnam was re-assigned to Quantico, Virginia as the Assistant Chief of Staff, G-5 Strategy and Plans Division at Training and Education Command.
On 10 July 2020, Colonel Wittnam will assume the duties as the Commanding Officer, Marine Corps Mountain Warfare Training Center.