Established in 1946, SAC really began its life in earnest when Curtis LeMay arrived as its chief in the , fall of 1948. He took over a force of 837 mostly aging aircraft and their ineffective crews. When he left in 1957 to become vice chief of staff of the Air Force, the numbers were 3,040 aircraft and 258,703 people. The bombers included 1,362 B-47s, 380 B-52s, and 22 of the older B-36s, as well as numerous tankers, transports, fighters, helicopters, and other support craft. Twenty percent of the bomber fleet was on “scramble"-style alert at all times, and a dozen bombers were always in the air to avoid any danger of being hit on the ground by a surprise attack. In addition to bases in Texas, Michigan, California, Arizona, Maine, Kansas, North Dakota, and Massachusetts, SAC bombers flew out of Guam, Greenland, North Africa, Spain, and England.
As Cold War tensions rose in the 1960s and ICBMs joined SAC’s forces, the number of nuclear warheads in SAC’s arsenal grew to more than 2,000. During the Berlin crisis, half the force went on ground alert; during the Cuban missile crisis, readiness was ratcheted up to the higher “defcon,” or defense condition, level, and the total number of bombers in the air increased from 12 to 66, many of them circling above the Mediterranean and North Atlantic as the leaders negotiated. By then SAC included 156 ICBMs on land (the United States also had 144 Polaris submarine-based missiles that LeMay had wanted to control) and 1,300 bombers. On September 27, 1991, SAC finally ended its roundthe-clock alert status. On May 31, 1992, it was deactivated, and its units were rolled into the new Air Combat Command.