The Strategic Air Command was a major part of the U.S. Air Force from 1946 until 1992. Its main mission was command and control of the United States land-based nuclear arsenal, which at first was carried exclusively in SAC's manned bomber force. As missile technology progressed and nuclear warheads became smaller, nuclear weapons were mounted on intermediate-range ballistic missiles (IRBM), later on intercontinental ballistic missiles (ICBM), and finally on cruise missiles which could be launched from ground sites, bombers, or ships.
As the successor to the heavy bomber wings that had (in Air Force mythology, anyway) won the war against the Axis powers in World War II, SAC had extremely high esprit d'corps, maintained by ruthless "zero defect" standards applied to personnel and equipment, and boldly stated in its motto, "Peace Is Our Profession", taken from SAC's primary mission of nuclear deterrence against the Soviet Union and (later) Communist China. These standards were somewhat justified by the sensitive political nature of nuclear weapons, but also provided a basis for generally excluding fighter pilots and other lesser beings from senior command positions in the Air Force. It is no coincidence that nearly all of the Air Force Chiefs of Staff served as CinCSAC before moving up to the top job at the Pentagon.
SAC also carried out conventional missions, mainly during the Vietnam when B-52 heavy bombers were deployed with conventional weapons to fly ARC LIGHT missions in support of Army units in South Vietnam and later (during the Nixon Administration) to carry out strategic bombing campaigns against North Vietnam. SAC bombers also saw (non-nuclear) actions during the First Gulf War.
After the fall of the Berlin Wall and the failure of the Russian Communist coup in 1991, SAC was broken up. Its bomber, strategic recon, and command assets went to the new Air Combat Command, its tankers were dispersed to the Air Mobility Command and to regional air forces, and its missile wings were eventually seconded to the Space Command after a brief period under the ACC.
Perhaps the best-known commander of SAC was General Curtis LeMay, who as commander of the Twentieth Air Force in World War II was responsible for the highly successful fire bomb attacks on Japan.