SAC Bombing and Navigation Competitions through the remainder of the 1950s, 1960s, 1970s and 1980s. Commencing in the late 1950s, in addition to representation from every SAC wing with a bombing and/or air refueling mission, later SAC competitions would also include participating bomber and aerial refueling units from the Royal Air Force's Bomber Command and (after 30 April 1968) its successor, RAF Strike Command. Nuclear Bunkers, SAC Ground Alert, and transfer of SAC's Fighter-Escort Wings It was described as the "Western Pentagon," specifically a, "...four-story, reinforced concrete and masonry office building..." above ground and a "...segregated, adjacent three-story below ground command post." This was the description of what would become Building 500 at Offutt AFB and the new headquarters complex built expressly for SAC, with construction commencing in 1955. SAC headquarters moved from the A Building at Offutt AFB to Building 500 in 1957. The underground nuclear bunker had 24-inch thick walls and base floor, 10-inch thick intermediate floors, and 24-to-42-inch thick roof. It also contained a war room with six 16-foot data display screens and the capacity to sustain up to 800 people underground for two weeks. The below ground bunker portion of the headquarters complex also contained an IBM 704 computer, which was used to develop monthly weather forecasts at targets, as well as for computing fuel consumption and fallout cloud patterns for planning strike routes and egress routes (e.g., determining the timing as to which targets to bomb first). In 1957, SAC also constructed The Notch, a facility alternatively known as the 8th Air Force Combat Operations Center (COC) and the Westover Communications Annex, since it was a sub-post of nearby Westover AFB. A 3-story nuclear bunker located on Bare Mountain, Massachusetts, The Notch was built with three-foot thick walls, 1.5 foot thick steel blast doors, and 20 feet underground to protect 350 people for 35 days. The Notch was shut down as a SAC facility in 1970 when 8th Air Force was relocated to Barksdale AFB, Louisiana. Despite this investment in "hardened" headquarters and command and control facilities, the 1957 Gaither Commission identified, "...little likelihood of SAC's bombers surviving [a Soviet first strike] since there was no way to detect an incoming attack until the first [Soviet nuclear weapon] warhead landed." As a result, SAC's bombers and tankers began sitting armed ground alert at their respective bases on 1 Oct 57. In another organizational change during