During the Cold War, rising tensions between the United States and the Soviet Union led both superpowers to rely heavily on nuclear arsenals as deterrents, and after the Soviet launch of Sputnik in October 1957, intercontinental ballistic missiles became a new and deadlier means of carrying nuclear warheads. Montana's missile field, a 23,500-square-mile area spanning nine counties, was the largest in the United States and at its height in the late twentieth century held 200 Minuteman missiles under the 341st Missile Wing at Malmstrom Air Force Base in Great Falls. This area was controlled by the 564th Missile Squadron, nicknamed "Deuce," which was responsible for five Minuteman missile alert facilities and fifty nuclear missile silos. The unit began as the 564th Bombardment Squadron during World War II, flying B-24 Liberators on missions in central and southern Europe, was reactivated by the Air Force as an ICBM squadron in 1965, became the first squadron in Montana to receive Minuteman II missiles in 1967, and had upgraded to Minuteman III ICBMs by 1975. The U.S.A.F. inactivated the 431st Missile Squadron and removed the Minuteman III missiles from their silos in 2008.