Sergeant Major David C. Hernandez was born in Los Banos, California. He enlisted and entered the United States Marine Corps on 15 October 2001 and underwent recruit training with Echo Company, 2nd Recruit Training Battalion, Marine Corps Recruit Depot, San Diego. Upon completion of recruit training, then Private First Class Hernandez attended the School of Infantry, where he attained the Military Operational Specialty of 0311, Rifleman.

In May of 2002, Sergeant Major Hernandez executed orders to Echo Company, 2nd Battalion 1st Marines, 1st Marine Division, Camp Pendleton, California. Initially, Sergeant Major Hernandez deployed on the 15th MEU in support of Operation Iraqi Freedom (OIF) in November of 2002. In September 2003 Sergeant Major Hernandez was promoted to Corporal. During February of 2004 he deployed in support of OIF to Al Fallujah, Iraq. During his tour with 2nd Battalion 1st Marines he served in a variety of billets to include riflemen, team leader, and infantry squad leader. In July 2005, Sergeant Major Hernandez was promoted to Sergeant.

In November 2005, Sergeant Major Hernandez was assigned to Weapons Field Training Battalion, Camp Pendleton, California. While at Weapons Field Training Battalion, Sergeant Major Hernandez served as a range coach, block non-commissioned officer, range staff non-commissioned officer, and as a primary marksmanship instructor.

In June 2008, Sergeant Major Hernandez, reported to Lima Company, 3rd Battalion, 5th Marines, 1st Marine Division, Camp Pendleton, California where he deployed on the 31st MEU in January of 2009. Sergeant Major Hernandez was promoted to Staff Sergeant in January of 2009. Sergeant Major Hernandez was re-assigned to Combined Anti-Armor Team (CAAT) One, Weapons Company, 3rd Battalion, 5th Marines and in September of 2010 he deployed with the Dark Horse Battalion to Sangin, Afghanistan in support of Operation Enduring Freedom. During this period he held the billets of a squad leader, section leader, platoon sergeant, CAAT platoon sergeant.

In August 2011, Sergeant Major Hernandez was assigned to Headquarters and Service Battalion, U.S. Marine Corps Forces Command
in Norfolk, Virginia where he served as the as the Operations Chief. In June 2012, Sergeant Major Hernandez was promoted to Gunnery Sergeant.

After completing Combat Instructors School in March 2014, Sergeant Major Hernandez was transferred for duty to Infantry Training
Battalion, School Of Infantry in Camp Pendleton, California. There he held the billets of a Combat Instructor and Chief Instructor.
Selected to First Sergeant in December of 2015, he was assigned as the Charlie Company, First Sergeant at Infantry Training Battalion.

In June 2017, Sergeant Major Hernandez received orders to Site Support, Green Bay to serve on Inspector-Instructor duty.

Sergeant Major Hernandez was frocked to his current rank in February 2021 and was transferred to Combat Logistics Battalion 5,
Combat Logistics Regiment 1 aboard Camp Pendleton CA to serve as the Battalion Sergeant Major.

Sergeant Major Hernandez is married to Melissa Hernandez and they have twin daughters Isabella and Emmalyn and their son
Alexander.

Sergeant Major Hernandez's personal awards include the Purple Heart Medal, Meritorious Service Medal, Navy and Marine Corps

Commendation Medal with Combat Distinguishing Device with one gold star, Navy and Marine Corps Achievement Medal and the
Combat Action Ribbon with one gold star.