Captain Murtagh graduated from Boston College in May 2009. In January 2012, he reported for training at Officer Candidate School, Quantico, VA and was commissioned a Second Lieutenant on 30 March 2012. Upon commissioning, he reported to Officer Selection Office Manhattan in New York, NY for two months prior to attending The Basic School (TBS). In June 2012, he reported to TBS. Following TBS, he reported to the Infantry Officer Course (IOC) and upon graduation received the Military Occupational Specialty (MOS) of 0302 – Infantry Officer.
In April 2013, Second Lieutenant Murtagh reported to Charlie Company, 1st Battalion, 25th Marines and was assigned the billet of Platoon Commander for First Platoon. In May 2013, Charlie Company was reflagged as Fox Company, 2nd Battalion, 25th Marines. During this time, Second Lieutenant Murtagh executed annual training events Operation Heavy Metal 13 at Fort Drum, NY and Operation Heavy Metal 14 at Fort AP Hill, VA. He also attended the Marine Forces Reserve CBRN Officer collateral duty course with 24th Marines in Kansas City, MO. In March 2014, he was promoted to First Lieutenant.
In July 2015, First Lieutenant Murtagh participated in annual training at Fort AP Hill, VA. Upon returning from this annual training he was assigned the billet of Weapons Platoon Commander and Fire Support Team (FiST) Leader. For a short time, he also served as acting Company Executive Officer. While serving as FiST Team Leader for Fox Company, he attended multiple Fire Support and Close Air Support Exercises at Warren Grove, NJ, Fort Indiantown Gap, PA, and Fort Dix, NJ. In May 2016, he was promoted to Captain.
Captain Murtagh continued in his role as FiST Team Leader for Fox Company. He attended the 25th Marines Fire Support Coordinators Course in January 2017 at Fort Devens, MA and participated in Operation Northern Strike 16 at Camp Grayling, MI and Integrated Training Exercise (ITX) 4-17 at Twentynine Palms, CA. Upon returning from ITX in June 2017, Captain Murtagh was assigned to Golf Company, 2nd Battalion, 25th Marines to transition into command of that unit.