In May 2008, Lance Corporal Martensson reported to 1st Reconnaissance Bn, Charlie Company where he served as the Assistant Radio Transmission Operator for 2nd Platoon, Team 3. During his time there, he was promoted to the rank of Corporal and deployed in support of Operation Iraqi Freedom to Al Assad, Iraq. Following his first deployment, he was promoted to the rank of Sergeant and assigned as the Assistant Team Leader. In 2010, Sergeant Martensson deployed again with Charlie Company to Helmand Province, Afghanistan in support of Operation Enduring Freedom.
In February 2011, Sergeant Martensson reported to Marine Corps Mountain Warfare Training Center (MCMWTC) in Bridgeport, CA and went through the requisite instructor schools to become a Formal School Instructor. During his time with Mountain Warfare Training Center, Sergeant Martensson taught at Unit Training Group, Summer Mountain Leaders Course, Winter Mountain Leaders Course, Scout Skiers, and Assault Climbers Course. Sergeant Martensson was also chosen to perform the duties of subject matter expert during the First Pitch portion of the Royal Marine Mountain Leaders Course in Lympstone, UK.
In March 2014, Sergeant Martensson executed orders to 3d Reconnaissance Bn where he was promoted to Staff Sergeant. Staff Sergeant Martensson served as Team Leader for 2nd Platoon, Alpha Company where he executed numerous deployments for training across Southeast Asia. Staff Sergeant Martensson was selected to become the Platoon Sergeant and subsequently the Platoon Commander of 3rd Platoon, Alpha Company where he led his platoon through multiple theater security exercises in South Korea, the Philippines, Malaysia, and Singapore.
In November 2017, Staff Sergeant Martensson reported to Force Reconnaissance Company, II MEF where he served as Assistant Platoon Sergeant and Team Leader for 1st Platoon. During his time as Team Leader, Staff Sergeant Martensson executed several deployments for training with U.S. Special Operations elements and partnered nations. In August 2018, he was promoted to the rank of Gunnery Sergeant and subsequently transferred to the position of Company Assistant Operations Chief receiving orders to return to MCMWTC in Bridgeport, California.
While at MCMWTC, Gunnery Sergeant Martensson served as the Staff Non-Commissioned Officer in Charge of the Reconnaissance and Surveillance Section from April 2019 through June 2020 before taking over as the Infantry Training Company Operations Chief from June 2020 to April 2022. Gunnery Sergeant Martensson supervised the training of Infantry Battalion leaders during the execution of Mountain Operations Special Planners Course, Summer/Winter Mountain Leaders Course, Mountain Scout Snipers Course, and the training of organic ground reconnaissance assets during the conduct of formal schools, as well as MAGTF War Fighting Exercises.
While aboard MCMWTC he was promoted to the rank of First Sergeant and subsequently issued orders to Fleet Antiterrorism Security Team, Company Pacific in Yokosuka, Japan. He reported to Fleet Antiterrorism Security Team Company, Pacific, where he served as Unit Senior Enlisted Leader from May 2022 to April 2025. First Sergeant Martensson received orders to Combat Logistics Battalion 4 aboard Camp Schwab in Okinawa, Japan where he served as the Motor Transportation Company, Unit Senior Enlisted until he was promoted to the rank of Sergeant Major on 19 March 2026.
His personal decorations include the Navy and Marine Corps Commendation Medal, the Navy and Marine Corps Achievement Medal, and the Combat Action Ribbon.