Mission Delta 2 (MD2) is the United States Space Force's space domain awareness delta, headquartered at Peterson Space Force Base, Colorado. Mission Delta 2 tracks and monitors all human made objects from low Earth orbit to geosynchronous orbit and further out to deep space. It also partners with the National Oceanic and Atmospheric Administration to provide weather satellite observation for the U.S. Armed Forces. It consists of the 15th Space Surveillance Squadron, 18th Space Defense Squadron, 19th Space Defense Squadron, and 20th Space Surveillance Squadron.
Mission Delta 2 was originally established on 1 February 1942 as the 21st Bombardment Group (21 BG), flying the B-25 Mitchell and B-26 Marauder in antisubmarine patrols during World War II. After the 21 BG inactivated in 1943, the 21st Fighter Group (21 FG) was activated in 1943 in Hawaii, flying the P-39 Airacobra, P-38 Lightning, and P-51 Mustang during the Battle of Iwo Jima and escorting bombers during air raids on Japan until the 21 FS was inactivated in 1946. The 21st was reactivated again in 1952 as the 21st Fighter-Bomber Group (21 FBG) under the 21st Fighter-Bomber Wing and flying the F-86 Sabre, deploying to support NATO forces in France during the Cold War before inactivating in 1958. Although the group would be redesignated the 21st Tactical Fighter Group (21 TFG) in 1985, it would not be reactivated until 1991 as the 21st Operations Group (21 OG), when it briefly was reactivated under the 21st Wing, providing air defense for Alaska flying the F-15C and F-15E, before inactivating later that year. The 21st Operations Group was reactivated under Air Force Space Command's 21st Space Wing in 1992 and provided missile warning, space surveillance, and space control forces. On 24 July 2020, it was redesignated as Space Delta 2 and transferred from the Air Force to the Space Force on 21 October 2020. On 31 October 2024 it was redesignated Mission Delta 2 and gained sustainment responsibilities, along with organic cyber defense and intelligence forces.
History Anti-submarine patrols in the American Theater
On 1 February 1942, the 21st Bombardment Group (Medium) was activated at Bowman Field, Kentucky under the United States Army Air Forces' Air Force Combat Command, flying the North American B-25 Mitchell medium bomber. It consisted of the 8th Reconnaissance Squadron (later redesignated the 398th Bombardment Squadron), 313th Bombardment Squadron, 314th Bombardment Squadron, and 315th Bombardment Squadron. On 6 February 1942, the 21st Bombardment Group moved to Jackson Army Air Base, Mississippi, serving as an operational training group. On 11 March 1942, it was realigned under the 3rd Air Force's III Bomber Command and on 21 April 1942 moved to Columbia Army Air Base. On 2 May 1942, it was briefly reassigned from III Bomber Command to XII Bomber Command, before being regained by III Bomber Command on 8 May 1942 and moved to Key Field, Mississippi on 24 May 1942. On 24 June 1942, the 21st Bombardment Group moved to MacDill Field, Florida and converted to Martin B-26 Marauder medium bombers. While stationed at MacDill Field, the group conducted anti-submarine patrols in the Caribbean Sea, participating in the American Theater of World War II. On 10 October 1943, the 21st Bombardment Group was inactivated.
Bomber escort and fighter operations in the Pacific Theater
On 31 March 1944, the 21st Fighter Group, Two Engine, was activated on 21 April at Wheeler Field, Hawaii and assigned to the US Army Air Forces, Central Pacific Area before being realigned under Seventh Air Force's VII Fighter Command on 24 April 1944. The 21st Fighter Group consisted of the 46th Fighter Squadron, 72nd Fighter Squadron, and 531st Fighter Squadron and flew the Bell P-39Q Airacobra. Tasked with providing air defense over the Hawaiian Islands, the 21st Fighter Wing was realigned under the 7th Fighter Wing on 3 July 1944 and began upgrading to the Lockheed P-38J/L Lightning in September 1944. In October 1944, the 21st Fighter Group switched aircraft again, flying the North American P-51 Mustang and transferring to Mokuleia Field, Hawaii on 13 October 1944. On 10 November 1944, the 21st Fighter Group was realigned under the VII Fighter Command, but remained attached to the 7th Fighter Wing until 28 February 1945.
In February 1945, the 21st Fighter Group was directly resubordinated under the VII Fighter Command and transported by ships to Iwo Jima, arriving at Central Field on 25 March 1945. On the Morning of 26 February 1945, the elements of the 21st Fighter Group was attacked by Imperial Japanese Army soldiers on the ground. Fighting alongside a contingent of U.S. Marines, the airmen killed 250 Japanese soldiers in tent-to-tent fighting, with fourteen 21st Fighter Group airmen killed and 50, including the group commander, Colonel Kenneth R. Powell, were wounded. Following the engagement on the ground, the 21st Fighter Group provided close air support for the remainder of the Battle of Iwo Jima.
Following the island's capture, the 21st Fighter Group began conducting long-range bomber escort missions, with the first occurring on 7 April 1945, where P-51 Mustangs from the group escorted B-29 Superfortress heavy bombers striking the Nakajima Aircraft Company in Tokyo. This mission was the first time bombers over Japan were accompanied by escort fighters and was the longest over-water fighter escort mission to that point during World War II. On 16 July 1945, the group transferred to Iwo Jima's South Field and flew its last combat mission over Japan on 14 August 1945. For its raid over Nakajima Aircraft Company, the 21st Fighter Group was awarded the Distinguished Unit Citation. After the end of World War II, the 21st Fighter Group transferred to Isely Field, Saipan on 4 December 1945 and then to Northwest Field, Guam on 17 April 1946. The 21st Fighter Group was inactivated on 10 October 1946.
NATO deployment to France
On 1 January 1953, the 21st was reactivated as the 21st Fighter-Bomber Group at George Air Force Base, California under the 21st Fighter-Bomber Wing. Following the end of World War II, the wing replaced the group as the primary unit of organization within the Air Force. Initially organized under Tactical Air Command's Ninth Air Force, the 21st Fighter-Bomber Group consisted of its World War II 72nd Fighter-Bomber Squadron and 531st Fighter-Bomber Squadron, adding the 416th Fighter-Bomber Squadron. Initially flying the F-51 Mustang fighter, within six months of activation, the 21st Fighter-Bomber Group had transitioned to the North American F-86F Sabre, a first-generation jet fighter. In September and October 1953, the 21st Fighter-Bomber Group participated in a special arctic warfare program at Eielson Air Force Base, Alaska. Following the completion of this exercise, it sent six F-86s to participate in Project Willtour, which consisted of an 11,000 mile tour of twelve Central, Caribbean, and South American countries. In April and May 1954, it participated in Operation Boxkite at North Field, South Carolina, testing the ability for a tactical wing to deploy to a forward location and sustain thirty days of combat operations.
Following the completion of these exercises, on 22 June 1954, the Secretary of the Air Force announced that the 21st Fighter-Bomber Wing, including the 21st Fighter-Bomber Group, would be deployed to Chambley Air Base, France, under Twelfth Air Force and the North Atlantic Treaty Organization to defend against the Warsaw Pact and Soviet Union. While the 21st Fighter-Bomber Wing's personnel moved in four tranches across air, land, and sea transport, the 21st Fighter-Bomber Group's F-86s flew directly, stopping in Labrador, Greenland, Iceland, and Scotland. The 21st Fighter-Bomber Group officially was stationed at Chambley Air Base on 12 December 1954, however the airfield could not handle the jet fighters until it was upgraded by Air Force engineers in June 1956. The flying elements of the group operated in the interim out of a variety of airfields in the French countryside.
One of the most notable pilots in the 21st Fighter-Bomber Group was then-First Lieutenant Michael Collins, who would later become a NASA astronaut, flying the Gemini 10 and Apollo 11 missions, before retiring from the Air Force as a major general.
The 21st Fighter-Bomber Group conducted close air support training with United States Army Europe land forces and took first place at the United States Air Forces in Europe's gunnery meet at Wheelus Field, Libya. In 1955, the 21st Fighter-Bomber Group participated NATO's Carte Blanche atomic warfare exercise and took second place at Nellis Air Force Base's gunnery exercise in 1956. The unit also won the United States Air Forces in Europe award for tactical proficiency in 1957. On 8 February 1958, the 21st Fighter-Bomber Group and 21st Fighter-Bomber Wing were inactivated.
Alaskan air defense operations
While the 21st Wing would continue, Air Force policy on operations groups resulted in the 21st Fighter-Bomber Group remaining inactive for the following decades. In 1985, it was redesignated as the 21st Tactical Fighter Group, but not activated until 25 September 1991 as the 21st Operations Group under the 21st Wing at Elmendorf Air Force Base, Alaska. It briefly consisted of the 21st Operations Support Squadron, 43rd Fighter Squadron, 54th Fighter Squadron, and 90th Fighter Squadron under Alaskan Air Command and supporting North American Aerospace Defense Command. The 43rd Fighter Squadron and 54th Fighter Squadron flew the McDonnell Douglas F-15C Eagle, while the 90th Fighter Squadron flew the McDonnell Douglas F-15E Strike Eagle. Following the 21st Operations Group's activation, the Air Force implemented a program that directed that each base would have one wing and one commander. The 21st Wing and 3rd Wing shared Elmendorf Air Force Base, resulting in the 21st Wing, and 21st Operations Group's inactivation on 19 December 1991.
From space surveillance to space control
On 15 May 1992, the 21st Operations Group was reactivated alongside the 21st Space Wing at Peterson Air Force Base under Air Force Space Command, with the 21st Operations Group specifically absorbing the responsibilities of the former 1st Space Wing. The 21st Operations Group's primary mission was missile warning. It operated the Defense Support Program missile warning constellation, which was flown by the 2nd Space Warning Squadron at Buckley Air National Guard Base and the 5th Space Warning Squadron at Woomera Air Station, Australia, while the 4th Space Warning Squadron operated the Mobile Ground Station from Holloman Air Force Base, before transferring the mission to the Air National Guard's 137th Space Warning Squadron in 1997. The 11th Space Warning Squadron was activated in 1994 at Falcon Air Force Base to operate the Attack and Launch Early Reporting to Theater (ALERT) missile warning system.