Gunnery Sgt. William Callen, the operations chief of

Gunnery Sgt. William Callen, the operations chief of the Marine Corps Martial Arts Center of Excellence in Quantico, Va., demonstrates knife techniques on 1st Sgt. Sigrid Rivera, Service Company first sergeant, Headquarters Battalion, Marine Corps Base Hawaii, during fourth-degree black belt training at the Staff Noncommissioned Officer Academy aboard MCB Hawaii, July 29, 2015. The Marine Corps Martial Arts Program directly supports the mission of Marine Corps Base Hawaii, which is to provide programs and services in direct support of units, individuals and families in order to enhance and sustain combat readiness for all operating forces and tenant organizations aboard MCB Hawaii. (U.S. Marine Corps photo by Cpl. Brittney Vito/Released)