The 3rd Air Division was formed in 1949 to control the deployments of B-29s to the UK. It was soon upgraded to the status of a major command, and became the Third Air Force in May 1951 as part of the United States Air Forces in Europe. SAC then formed the 7th Air Division to control the nuclear bomber deployments. In fulfilment of NATO's plans to halt a Soviet invasion of Western Europe using tactical nuclear weapons, the 3rd Air Force received its own nuclear weapons when the 20th Fighter Wing deployed to RAF Wethersfield in Essex on 1 June 1952, with Republic F-84F Thunderstreak fighters and Mark 7 nuclear bombs. It reequipped with the North American F-100 Super Sabre in 1957, and the General Dynamics F-111 in 1970. The US Navy's Polaris ballistic missile submarines arrived at Holy Loch in Scotland in March 1961.