Lieutenant Colonel Fennell was commissioned a 2nd Lieutenant after graduating from Officer Candidate School in 1997. Under a law contract, he went on to complete his law and master’s degrees before graduating from The Basic School in 2001. He graduated with honors from the Naval Justice School and was stationed at Marine Corps Base Hawaii in 2002 where he served as Officer in Charge of Legal Assistance and as a Military Justice federal prosecutor. In 2004, Captain Fennell was honorably discharged whereupon he returned to private practice as a law firm associate attorney.
In 2006, hearing the call to serve in the War on Terror, Captain Fennell entered the Selected Marine Corps Reserve to join Marine Air Control Squadron 23 (MACS-23) in its upcoming deployment to Iraq. In 2007, he left civilian employment to complete the Air Defense Control Officer Course before deploying to Al Asad, Iraq in 2008 as Detachment Commander of the Tactical Air Operations Center (TAOC). He presented air command and control briefs on behalf of MACG-38 at U.S. Air Force Central Command in Qatar and on behalf of 3D MAW at the Weapons and Tactics conference in Bahrain. Upon returning to the states in 2009, he was assigned Executive Officer of MACS-23.
Later in 2009, Major Fennell joined 4th Civil Affairs Group to lead a civil affairs team in Helmand Province, Afghanistan. His team supported 3rd Battalion 10th Marines at Firebase Fiddlers Green in the shaping of Marjah before being re-assigned to 1st Battalion 6th Marines for Operation Moshturak. Major Fennell led his team in the initial nighttime helicopter assault of Marjah on February 13, 2010 and remained there until June 2010. He was invited to brief an audience of international senior leaders at the Afghanistan Counter Insurgency Academy in Kabul, Afghanistan.
In 2010, Major Fennell returned to MACS-23 and served as TAOC Detachment Commander during Exercise Northern Edge at Eielson Air Force Base, Alaska. In 2011 Major Fennell again served as Executive Officer, MACS-23 until the unit’s deactivation in September 2012. Combat Logistics Battalion 453 was activated in its place and Major Fennell was asked to remain as Executive Officer, CLB-453.
From 2013 to 2015, Lieutenant Colonel Fennell served as an Operations Watch Officer with U.S. Strategic Command, Joint Functional Component Command for Integrated Missile Defense (JFCC-IMD). In 2015, he was certified in MAGTF Information Operations and joined Marine Forces Pacific as the Information Operations Staff Officer where he supported U.S. Pacific Command exercises Pacific Sentry and Cobra Gold, Thailand. He assumed command of Marine Tactical Air Command Squadron 48 in April 2017.
Lieutenant Colonel Fennell holds a B.S. degree from Colorado State University, M.S.E.L degree magna cum laude from Vermont Law School, and J.D. degree from Lewis and Clark Law School. He is a 2012 graduate of Marine Corps Command and Staff College. He volunteers his time at his local church and a local senior care center.