After the 1948 Berlin Blockade and the 1950 invasion of South Korea by the Korean People's Army, the perceived threat from the Soviet Union rose. On 23 April 1951, RAF Greenham Common was made available to the United States Air Force by the British Ministry of Defence as a Strategic Air Command base, with joint operations with the Royal Air Force units. Formal handover to the 7th Air Division was on 18 June and massive reconstruction work began. Basically, the entire wartime airfield was demolished and replaced with a new 10,000 ft (3048 m) east–west runway with parallel taxiways north and south of it leading to extensive hardstandings. A new technical and domestic site was built to the south of the runway, involving diversion of the A339 road and demolition of several homes and two pubs. Construction work was finally completed and the base declared operational in September 1953.