was not a sufficient defense; and at the request of NATO, Iceland entered into a defense agreement with the United States directly. This was the beginning of the Iceland Defense Force. Over the next four decades, the Defense Force was "at the front" of the Cold War and was credited with playing a significant role in deterrence. On 25 May 1951 the United States Air Force (USAF) reestablished its presence at Keflavik Airport with the stationing of the 1400th Air Base Group. Jurisdiction of the airport was assumed by Military Air Transport Service (MATS). MATS re-established a military air terminal and refueling point for trans-Atlantic air service between the United States and Europe at Keflavik. MATS (later Military Airlift Command and Air Mobility Command) units remained at the airport until the withdrawal of United States military units from Iceland in 2006. During 1947–51, while the base was operated by a U.S. civilian contractor company most of the World War II temporary structures were left empty and became badly deteriorated. The airfield complex, one of the largest in the world during the war, also required upgrading to accommodate modern aircraft. The contractor had extended one runway, constructed a new passenger terminal and hotel building, one aircraft hangar, a hospital, housing units and other facilities for the staff. But this was insufficient for the new Defense Force, so additional facilities had to be provided quickly. A crash reconstruction program was initiated and temporary housing was erected during the construction of permanent housing. The airfield was extended by the Nello L. Teer Company and two new aircraft hangars were constructed. Most of this work was completed by 1957. Soon after the return of U.S. forces to Keflavik. Air Defense Command (ADC) established a temporary radar station at the airport, equipped with World War II-era AN/TPS-1 and AN/TPS-3A radars that operated until a permanent radar station could be constructed at nearby Rockville AS. Between 1952 and 2006, Air Forces Iceland provided air defense for Iceland, operated Keflavik Airport, and furnished base support for all U.S. military forces in Iceland participating in its defense under NATO. Also Air Force component of NATO Iceland Defense Force. ADC, later renamed Aerospace Defense Command used the facility for air surveillance of Iceland and the North Atlantic, employing F-102 Delta Dagger and then F-4C Phantom II fighters as interceptors. Over 1,000 intercepts of Soviet aircraft took place inside Iceland's