Lieutenant Colonel Donlin was commissioned as a Second Lieutenant in the United States Marine Corps in August 2005 through the Officer Candidates Course and reported to The Basic School in Quantico, Virginia. In March 2006, he reported to Pensacola, Florida for primary flight training at Naval Air Station (NAS) Whiting Field. He then reported to NAS Meridian, Mississippi in April 2007 for advanced jet training.
He was designated as a Naval Aviator in May 2008, and reported to Marine Corps Air Station Cherry Point, North Carolina for training in the AV-8B Harrier. In 2009, Captain Donlin reported to Marine Attack Squadron (VMA) 223, MCAS Cherry Point, for duty as an AV-8B Harrier pilot while also serving as the Airframes Division Officer. In 2010, he joined VMA-542 and deployed in support of the 31st Marine Expeditionary Unit in Southeast Asia. While in VMA-542, he served as the Squadron Logistics Officer and Powerline Division Officer.
In 2012, Captain Donlin reported to Naval Base Little Creek, Virginia for Tactical Air Control Party training, becoming a Joint Terminal Attack Controller/Forward Air Controller (JTAC/FAC). He then reported to 2D Tank Battalion, Camp Lejeune, North Carolina for duty as a Forward Air Controller; deploying with Bravo Company to Afghanistan in support of Operation Enduring Freedom.
In 2013, Captain Donlin was selected on the Commandant’s Career Level Education Board (CCLEB) for the Marine Corps' Secondary Education Program (SEP), Leadership Education and Development (LEAD) specialty at the United States Naval Academy (USNA), earning a Masters in Leadership Education and Development. He then served as the Company Officer for 28th Company and Executive Officer for 6th Battalion, USNA.
In July 2016, Major Donlin was selected to transition to the 7315 PMOS, UAS Officer. He reported to VMU-2 in August 2016, where he served as the Operations Officer, Aircraft Maintenance Officer, and Executive Officer.
In July 2019, Major Donlin reported to II Marine Expeditionary Force Command Element where he served as the UAS Integration Officer and II MEF Exercise Director.
Lieutenant Colonel Donlin's awards include the Meritorious Service Medal with gold star, the Navy and Marine Corps Commendation Medal with Valor device and gold star, the Navy and Marine Corps Achievement Medal, Combat Action Ribbon, and various campaign, service, and unit awards.