Colonel Hollahan was born in North Carolina in 1965, but grew up in Decatur, Georgia. He was commissioned a Second Lieutenant following graduation from The Citadel in 1988. Upon graduation from The Basic School and Motor Transport Officer's Course, he was assigned to Truck Company, 1st Marine Division as Platoon Commander and the Company Executive Officer and at Camp Pendleton, California.

In 1990, Colonel Hollahan became the Company Commander of Truck Company, 1st Marine Division, during Operation Desert Storm. In 1991, he served as the Motor Transport Officer for 1st Light Armored Infantry Battalion, Camp Pendleton, CA. In 1992, Colonel Hollahan became an Instructor and The Motor Transport Officer at The Basic School. Following completion of the Amphibious Warfare School in Quantico, V.A. in 1995, Colonel Hollahan was assigned to 8th Motor Transport Battalion as the Headquarters and Service Company Commander and the General Support Company Commander at Camp Lejeune, N.C. During this tour, he was selected as CSSD-28’s S-3 Operations Officer and deployed with Special MAGTF Assured Response to relieve 22nd MEU(SOC) at the American Embassy in Monrovia Liberia.

Upon return to 2d FSSG, Colonel Hollahan was again assigned to 8th Motor Transport Battalion, this time to serve as the S-4. In 1997, he was assigned to MSSG-26 as the S-3 Operations Officer in support of 26th MEU(SOC). During this deployment, he participated in numerous NATO and other bilateral exercises, and the first deployment of the MEU as the NATO Strategic Reserve into Bosnia-Herzegovina. He was selected and promoted to Major during this deployment.

In 1998, he was transferred to Manpower and Reserve Affairs Department, Headquarters Marine Corps, where he served as Head, Combat Service Support Enlisted Assignments Section (MMEA-83), and Assistant Branch Head, Enlisted Assignments Branch (MMEA-8A).

He completed the USMC Command and Staff Seminar Course and the Advanced Logistics Officer Course during this tour. Upon a successful tour at Headquarters Marine Corps, Colonel Hollahan was transferred to 2d Marine Division, where he served as Division Motor Transport Officer, and S-4 Logistics Officer of the Fighting 6th Marines. He deployed to Bridgeport, California and Exercise Battle Griffin/Strong Resolve in Norway as the Arrival/Assembly Operations Group Operations Officer in support of MAGTF 2. During his tour with 2d Marine Division Colonel Hollahan attended the Maritime Pre-Positioning Force Staff Planning Course.

In 2003, Colonel Hollahan became the Logistics Plans Branch Head, G-4, III Marine Expeditionary Force, where he participated in the re-write of the Korean family of Plans and numerous bilateral exercises; Ulchi Focus Lens and RSOI/Foal Eagle. During June 2004 he was transferred to the Pentagon and assumed the billets as Chief, Exercises and Wargames, and Plans / Readiness Branch Chief for the J4, The Joint Staff, Washington D.C.

In 2006, Colonel Hollahan became the Commanding Officer of Combat Logistics Battalion 22 (CLB 22), supporting 22nd MEU in EUCOM, CENTCOM and PACOM AOR. After completion of his tour with CLB 22, Colonel Hollahan became the Assistant Chief of Staff, G-3 for 2d Marine Logistics Group (MLG) following on to become the Chief of Staff for 2d MLG.

In 2008, Colonel Hollahan attended the Naval War College, Newport, RI, where he earned his Masters Degree in National Security Strategic Studies and completed Joint and Combined Warfighting School (JPME II) in 2009.

After receiving his Masters, Colonel Hollahan was assigned as the Ground Colonel’s Monitor, Marine Manpower Officer Assignment, Manpower and Reserve Affairs, Headquarters Marine Corps

In June 2010, Colonel Hollahan assumed duties as Commanding Officer, Combat Logistics Regiment 27, 2d MLG. During this time, Colonel Hollahan deployed in support of Operation Enduring Freedom as the Chief of Staff, 2d Marine Logistics Group (FWD) and upon redeployment, served as the Commander, 2d Marine Logistics Group (FGE), until returning to the Regiment in March 2012.