Sergeant Major Callahan is a native of Covina, California. He enlisted in the Marine Corps on 4 March 1985. Upon completion of recruit training, MCRD, San Diego, CA in May 1985, Private Callahan was assigned to Military Postal School, Fort Benjamin Harrison, Indianapolis, IN. In August 1985, Private Callahan was assigned to the Military Post Office, 3d Force Service Support Group, Camp Foster, Okinawa, Japan where he performed duties as a Military Postal Clerk.
In July 1986, Lance Corporal Callahan transferred to the First Force Service Support Group, Marine Corps Base Camp Pendleton, CA where he performed duties as Military Postal Clerk.
In August 1988, Corporal Callahan was assigned to the Meu Service Support Group Fifteen, Marine Corps Base Camp Pendleton, CA where he performed duties as Military Postal Clerk.
In August 1990, Corporal Callahan was assigned to the First Force Service Support Group, Marine Corps Base Camp Pendleton, CA where he performed duties as Military Postal Clerk, and was deployed with Brigade Service Support Group Five to Desert Shield/Desert Storm.
In April 1993, Sergeant Callahan was accepted to Drill Instructor School, Marine Corps Recruit Depot, San Diego, CA. Upon graduation in June 1993, he was assigned to India Company, Third Recruit Training Battalion, where he served three cycles as a Drill Instructor and three cycles as a Senior Drill Instructor.
In January 1996, Sergeant Callahan was assigned to First Service Support Group where he performed duties as Custodian of Postal Effects, SNCOIC of Military Post Office Kinser, and Postal Inspector.
In January 1998, Staff Sergeant Callahan reported to Third Force Service Support Group, Okinawa, Japan where he performed duties as Custodian of Postal Effects, SNCOIC of Camp Foster Post Office, and Postal Inspector for the Far East Commands.
In September 2003, Gunnery Sergeant Callahan reported to Postal School, Fort Jackson, SC where he performed duties as the Senior Enlisted Instructor for the Department of Defense Postal Section and Company First Sergeant for the Marine Detachment.
In February 2005, First Sergeant Callahan was assigned to Weapons and Field Training Battalion, Parris Island, SC where he performed duties as the First Sergeant of Field Training Company.
In January 2007, First Sergeant Callahan was assigned to Recruit Training Regiment, Marine Corps Recruit Depot, Parris Island, SC where he performed duties as the Company First Sergeant for India Company Third Recruit Training Battalion.
In January 2008, First Sergeant Callahan was assigned to 1st Battalion 3d Marines where he performed duties as the First Sergeant of Headquarters and Service Company and deployed to OIF in August 2008.
In April 2009, First Sergeant Callahan upon return from deployment performed duties as the First Sergeant of Weapons Company 1st Battalion 3d Marines until being promoted to his current rank.
In February 2010, Sergeant Major Callahan was assigned as the Inspector-Instructor Sergeant Major, 3d Battalion 23d Marines, Naval Air Station, Joint Reserve Base, New Orleans, LA.
Sergeant Major Callahan assumed his current position as the Battalion Sergeant Major, Combat Logistics Battalion Thirteen, First Marine Logistics Group in December 2012.
Sergeant Major Callahan’s personal decorations include: The Meritorious Service Medal in lieu of one gold star, Navy and Marine Corps Commendation Medal in lieu of one gold star, Army Commendation Medal, Navy and Marine Corps Achievement Medal in lieu of two gold stars, and the Drill Instructor Ribbon. He holds an Associate in Arts Degree with a Major in Business Management from Northwood University.
Sergeant Major Callahan is married to the former Luzchona Canete of Santa Rita, Philippines, they have three sons.