Korean War federalization

With the surprise invasion of South Korea on 25 June 1950, and the regular military's complete lack of readiness, the ANG was mobilized into federal active duty. The 122nd Bombardment Squadron was federalized and ordered to active duty on 1 April 1951. By then most of the squadron's aircraft and many of its pilots had already been transferred to active-duty units and sent to Japan as replacement and reinforcing aircraft for B-26 units engaged in combat.

The squadron was transferred to Langley Air Force Base, Virginia as part of Ninth Air Force, Tactical Air Command (TAC). The 122d became part of the 4400th Combat Crew Training Group, a temporary organization formed by TAC with the mission of training pilots in the B-26 for subsequent deployment to the war zone. The 122d was joined by the Pennsylvania Air National Guard's 117th Bombardment Squadron. On 1 November 1952 the training unit at Langley was inactivated and returned to Louisiana State Control on 1 January 1953.

Tactical Bomber mission

Following the end of the Korean War, the B-26s began to be withdrawn from active service and replaced by jet-powered equipment such as the Martin B-57 Canberra and the Douglas B-66 Destroyer. The 122nd was re-equipped with former active-duty B-26s and continued training with the versatile light bomber under the Texas Air National Guard's 136th Fighter-Bomber Wing, being operationally gained by TAC.

Air Defense mission

122nd Fighter-Interceptor Squadron F-102A Delta Dagger^{[lower-alpha 3]}

In 1957, the 136th Fighter-Bomber Wing was transferred from TAC to Air Defense Command (ADC), being re-designated as an Air Defense Wing. The B-26s were sent to storage at Davis-Monthan Air Force Base, Arizona (many would be later used in the Vietnam War as counter-insurgency aircraft), and the 122nd was redesignated as a Fighter-Interceptor Squadron on 1 June 1957. With the transfer to ADC, the 122nd was initially equipped with some obsolete Lockheed F-80 Shooting Stars|(F-80As modified to F-80C standards) Shooting Stars as an interim aircraft, receiving North American F-86D Sabres in late 1957 and lastly the upgraded F-86L Sabre at the end of the year with uprated afterburning engines and new electronics.

With the F-86L, the squadron was selected by ADC to man a runway alert program on full 24-hour basis – with armed jet fighters ready to "scramble" at a moment's notice. This event brought the squadron into the daily combat operational program of the USAF, placing it on "the end of the runway" alongside regular USAF-Air Defense Fighter Squadrons.

In 1958, the 122nd was authorized to expand to a group level, and the 159th Fighter Interceptor Group was established on 1 April 1958. The 122nd becoming the group's flying squadron. Other support squadrons assigned into the group were the 159th Materiel Squadron, 159th Air Base Squadron, and the 159th USAF Dispensary.

In July 1960, the 159th converted to the Convair F-102 Delta Daggers. In 1962, the 122nd Fighter-Interceptor Squadron was assigned to the Gulfport Combat Readiness Training Center, Mississippi, for six weeks of intensive flying training. Involved were 150 officers and airmen, including support elements from the 159th Consolidated Aircraft Maintenance Squadron, 159th Supply Squadron and 159th Air Base Squadron.

Tactical Air Command

Squadron F-100D Super Sabre^{[lower-alpha 4]}

In December 1970 the 159th was transferred from ADC to TAC. ADC was phasing down its manned interceptor force as the chances of a Soviet Bomber attack on the United States seemed remote. The unit was redesignated the 122nd Tactical Fighter Squadron and re-equipped with North American F-100 Super Sabres. In 1970, the F-100 was still considered a first-line aircraft, and most of the F-100s in the inventory were serving in South Vietnam flying combat missions. The Super Sabres received by the 122d came from the 20th Tactical Fighter Wing, which was transitioning to the General Dynamics F-111F. With the conversion to the F-100s, the ADC 24-hour alert status ended and retraining in tactical fighter missions began.

The 122nd flew the F-100s for almost a decade, retiring the aircraft beginning in April 1979 when the 122nd began receiving McDonnell F-4C Phantom II aircraft from active-duty units. In 1979 ADC was inactivated, with TAC taking over the Continental US Air Defense Mission. The 159th Group was assigned to Air Defense, Tactical Air Command (ADTAC), a named unit at the Numbered Air Force level under TAC. Under ADTAC, the 122nd began to fly air defense missions again with the Phantom II, although the squadron continued to fly tactical fighter training missions with the Phantom.

122nd F-4C Phantom II^{[lower-alpha 5]}

The Phantoms were ending their service life in the mid-1980s, and in 1986, the F-4Cs were replaced by McDonnell F-15A Eagles. As the F-15s had no tactical bombing capability at the time, the 122d continued the air defense mission under TAC.

Modern era

In March 1992 the 159th Tactical Fighter Group became the 159th Fighter Group when the unit adopted the USAF Objective Organization, and the 122nd Fighter Squadron was assigned to the new 159th Operations Group. Later in June, TAC stood down and most of its units transferred to by Air Combat Command. No change in mission was made and the 159th continued in the air defense role.

In the early 1990s, squadron aircraft and personnel were deployed to Aviano Air Base, Italy, flying combat missions over the former Yugoslavia during the Kosovo War as part of Operation Allied Force. On 11 October 1995, in accordance with the "one base-one wing" policy, the 159th Fighter Group was redesignated as the 159th Fighter Wing.

In mid-1996, the Air Force, in response to budget cuts, and changing world situations, began experimenting with Air Expeditionary organizations. The Air Expeditionary Force (AEF) concept was developed that would mix Active-Duty, Reserve and Air National Guard elements into a combined force. Instead of entire permanent units deploying as "Provisional" as in the 1991 Gulf War, Expeditionary units are composed of "aviation packages" from several wings, including active-duty Air Force, the Air Force Reserve Command and the Air National Guard, would be married together to carry out the assigned deployment rotation.

In the late 1990s, the 122nd Expeditionary Fighter Squadron was activated on several occasions, sending packages of personnel and aircraft to Incirlik Air Base, Turkey, to fly Combat Air Patrol missions over Iraq as part of Operation Northern Watch. Also the 122nd EFS was activated with a deployment to Prince Sultan Air Base, Saudi Arabia, flying CAP missions over Southern Iraq as part of Operation Southern Watch.

In response to the 9/11 attacks in 2001, the 122nd Fighter Squadron engaged in Combat Air Patrols over major United States Cities as part of Operation Noble Eagle (ONE). ONE patrols continued into 2002 before being scaled down.

In 2006, the F-15A models were retired and the 122nd was upgraded to the more capable F-15C Eagle. As part of the Global War on Terrorism, the 122nd EFS has been deployed to support Operation Iraqi Freedom (OIF); Operation Enduring Freedom (OEF) in Afghanistan, Operation New Horizons in Central and South America and Operation New Dawn in Afghanistan.

The most recent deployment of the 122nd Expeditionary Fighter Squadron was completed in October 2012 when the squadron deployed to at Al Dhafra Air Base, United Arab Emirates, and as part of the 380th Expeditionary Operations Group, the 122nd EFS flew missions in support of the joint air defense of the Persian Gulf and Operation Enduring Freedom. The mission included providing air superiority in support of national military objectives and flying fighter integration sorties with F-22 Raptors and McDonnell Douglas F-15E Strike Eagles.