Major General Hermesmann is a graduate, with honors, of Rutgers University. He was commissioned a second lieutenant in 1985.
During his initial tour on active duty, he served as a Company Commander, Series Officer, Special Assistant United States Attorney, Trial Counsel on behalf of the U.S. Government, and Defense Counsel. After being discharged from active duty he next served with 6th Motor Transport Battalion, 4th FSSG, Red Bank, New Jersey, as the Assistant Operations Officer, Operations Officer, and Executive Officer.
He assumed command of 6th Motor Transport Battalion in 2002. He was activated in January 2003 with 6th Motor Transport Battalion, "The Baghdad Express," commanding the battalion in combat operations during the initial invasion of Iraq. After his discharge from active duty, he continued to serve as Battalion Commander until 2004. He was next assigned as a Senior MORDT Inspector for Marine Corps Mobilization Command, Kansas City. He then served as the Future Operations Officer, 4th Marine Logistics Group (4th MLG), New Orleans. In 2007, he assumed command of 4th MLG, Forward East, Camp Lejeune, North Carolina. After relinquishing command, he was assigned as the AC/S, G-3/5, 4th MLG.
He next served as the Deputy Commander, 4th MLG, New Orleans from 2010 to 2012. In 2012, he was activated, serving initially as Vice Chief of Staff and then Chief of Staff, Marine Forces Reserve, New Orleans. He was selected for promotion to Brigadier General in 2014, and assigned as the Commanding General, 4th MLG. He concurrently served as Deputy Commanding General - Support, Marine Forces Korea. In 2016, he transferred to U. S. Marine Corps Forces Command, Norfolk, Virginia, where he served as Deputy Commanding General (Mobilization). He concurrently served as Deputy Commanding General - Support, Marine Forces Europe. He next served as the Director of Reserve Affairs, Headquarters Marine Corps. He next served as the Commander, U.S. Marine Corps Forces Korea, relinquishing command on 31 May 2019..
Major General Hermesmann has also earned a Masters of Strategic Studies from U.S. Army War College, and a Juris Doctorate degree from The University of Toledo College of Law. He is also a graduate of USMC Command and Staff College and Joint Forces Staff College.