Question: Marine Aviation Training Support Group 21 was reactivated when which Navy base near Warrington was renamed?

Context paragraphs:
Marine Aviation Training Support Group 33: Marine Aviation and Training Support Group 33 (MATSG-33) is a United States Marine Corps aviation training group that was originally established during World War II as Marine Aircraft Group 33 (MAG-33).  Fighter squadrons from MAG-33 fought most notably during the Battle of Okinawa and also as the first Marine aviation units to support the Korean War when they arrived as part of the 1st Provisional Marine Brigade.  They helped stabilize the United Nations positions during the Battle of Pusan Perimeter and fought in Korea for the remainder of the war.  At some point in the 1960s, the group was deactivated and was not reactivated until 2000, when Marine Aviation Training Support Group at Naval Air Station Oceana, Virginia was renamed MATSG-33.

Marine Air, West Coast: Marine Air, West Coast (MarAirWest) was a United States Marine Corps aviation training and administrative command established on 22 January 1943, which was responsible for the administration, training and equipment of the Marine Aviation Units on the West Coast during World War II.

VMFA-212: Marine Fighter Attack Squadron 212 (VMFA-212) was a United States Marine Corps F/A-18 Hornet squadron.  Most recently known as the "Lancers", the squadron was last based at Marine Corps Air Station Iwakuni, Japan and fell under the command of Marine Aircraft Group 12 (MAG-12) and the 1st Marine Aircraft Wing (1st MAW).  Due to a re-organization within Marine aviation, the squadron was deactivated in 2008.  It is scheduled to be reactivated as an MV-22B squadron in 2019 under MAG 26 at MCAS New River, NC.

16th Aviation Brigade (Australia): The 16th Aviation Brigade (16 Avn Bde) commands all the Australian Army aviation units and has technical control of the Army Aviation Training Centre reporting to Forces Command.  The Brigade was formed on 2 April 2002 by combining Headquarters Divisional Aviation (Operational Command) and Headquarters Aviation Support Group (Technical Command) and is headquartered in Enoggera Barracks, Queensland.  It was originally named Headquarters 16th Brigade (Aviation) and was renamed to the 16th Aviation Brigade.

Marine Aviation Training Support Group 22: Marine Aviation Training Support Group 22 (MATSG-22) is a United States Marine Corps aviation training group that was originally established during World War II as Marine Aircraft Group 22 (MAG-22).  Squadrons from MAG-22, were decimated at the Battle of Midway and after reconstituting fought during the Battle of Okinawa.  The group was deactivated following the end of the war and were not reactivated until May 1, 2000 when the Marine Aviation Detachment at Naval Air Station Corpus Christi, Texas was renamed MATSG-22.

Marine Aviation Logistics Squadron 42: Marine Aviation Logistics Squadron 42 was a reserve aviation logistics support unit of the United States Marine Corps.  They fell under the command of Marine Aircraft Group 42 and 4th Marine Aircraft Wing and were based at Naval Air Station Atlanta.  MALS-42 provided direct support to VMFA-142 and HMLA-773 and Navy squadrons VAW-77 and VR-46 and indirect support to two tactical Marine squadrons HMLA-773 Det A and HMM-774.  Due to a re-organization within Marine aviation, MALS-42 was deactivated in 2008.

Marine Aviation Training Support Group 53: Marine Aviation Training Support Group 53 (MATSG-53) is a United States Marine Corps aviation training group located at Naval Air Station Whidbey Island, Washington.  The group was originally established on April 1, 1943 as Marine Aircraft Group 53, the first Marine night-fighter group.

Marine Aviation Training Support Group 21: Marine Aviation and Training Support Group 21 (MATSG-21) is a United States Marine Corps aviation training group that was originally established in 1922 as the 2nd Aviation Group.  During World War II the unit was known as Marine Aircraft Group 21 (MAG-21).  Squadrons from MAG-21 fought in many of the opening battles of the war to include the Battle of Wake Island, Battle of Midway and as part of the Cactus Air Force during the Battle of Guadalcanal The group was deactivated following the end of the war and was not reactivated until 2000 when the Marine Aviation Detachment at Naval Air Station Pensacola, Florida was renamed MATSG-21.  The core of the MATSG personnel is derived from 175 officer instructors and 550 student naval aviators/naval flight officers.

Marine Aviation Training Support Group 23: Marine Aviation Training Support Group 23 (MATSG-23) is a United States Marine Corps aviation training group originally established during World War II as Marine Aircraft Group 23 (MAG-23).  Squadrons from MAG-23, augmented by Navy and Army flying units formed the Cactus Air Force during the Battle of Guadalcanal.  Since then it has evolved into the first Aviation Logistics focused Colonel level command, and serves as a functional training advocate for all USMC Aviation Logistics entry-level training.  The instructors and support staff of MATSG-23 are responsible for training thousands of Marines per year in the disciplines required to enable the expeditionary aviation required to support the Marine Air Ground Task Force.

Naval Air Station Pensacola: Naval Air Station Pensacola or NAS Pensacola (IATA: NPA, ICAO: KNPA, FAA LID: NPA) (formerly NAS/KNAS until changed circa 1970 to allow Nassau International Airport, now Lynden Pindling International Airport, to have IATA code NAS), "The Cradle of Naval Aviation", is a United States Navy base located next to Warrington, Florida, a community southwest of the Pensacola city limits.  It is best known as the initial primary training base for all U.S.Navy, Marine Corps and Coast Guard officers pursuing designation as Naval Aviators and Naval Flight Officers, the advanced training base for most Naval Flight Officers, and as the home base for the United States Navy Flight Demonstration Squadron, the precision-flying team known as the Blue Angels.

Supporting paragraphs: Marine Aviation Training Support Group 21 Naval Air Station Pensacola
Answer: Naval Air Station Pensacola