Maj Harb was commissioned in January 2012 upon graduation from Brevard College. After completing The Basic School and Infantry Officers Course, he was assigned to 1st Battalion, 3d Marines, where he served as a Rifle Platoon Commander and Company Executive Officer. During this tour, he deployed twice to the Indo-Pacific as part of the Unit Deployment Program, conducting theater security cooperation exercises in New Caledonia, the Republic of Korea, and Japan.

In 2016, Maj Harb was assigned to the Defense POW/MIA Accounting Agency where he served as the Officer in Charge of the Mountain Operations Section. In this capacity, Maj Harb deployed extensively throughout the Indo-Pacific region to recover the remains of US servicemembers still missing in action from WWII and the Vietnam War. Maj Harb has led alpine mountaineering expeditions in the Indian Himalayas, littoral operations throughout the islands of Papua New Guinea, and conducted jungle operations throughout Southeast Asia.

In 2019, Maj Harb reported to 3d Battalion, 8th Marines where he served as the assistant operations officer and the commanding officer of Company K. During his time with 3d Battalion, 8th Marines, Maj Harb conducted two MAGTF Warfighting Exercises aboard Marine Corps Base 29 Palms as well as deployed the company to Okinawa as part of the Unit Deployment Program.

In 2021, Maj Harb reported to Combat Development & Integration where he worked on Force Design initiatives, including the development of littoral maneuver and reconnaissance/counter-reconnaissance capabilities in support of the stand-in force concept. From 2022-2023 he served as the aide-de-camp to the Deputy Commandant, CD&I.

Maj Harb is a distinguished graduate of The Basic School, Expeditionary Warfare School and the Command and Staff College. He is also an Operations and Tactics Instructor and a fully qualified Marine Corps Mountain Leader.