(SAC) began to disperse its Boeing B-52 Stratofortress bombers over a larger number of bases, thus making it more difficult for the Soviet Union to knock out the entire fleet with a surprise first strike. SAC bases with large concentrations of bombers made attractive targets. SAC's response was to break up its wings and scatter their aircraft over a larger number of bases. As part of this program, it established the 4042d Strategic Wing at the new K. I. Sawyer Air Force Base, Michigan in August 1958. By 1961, the base was ready to accept the B-52s of the 526th Bombardment Squadron, which moved to K.I. Sawyer from Homestead Air Force Base, Florida. However, the 4042d Wing was a Major Command controlled (MAJCON) wing, which could not carry a permanent history or lineage, and SAC wanted to replace it with a permanent unit. The 410th Bombardment Wing was activated to replace the 4042d Wing in February 1963, The 644th, once again a bombardment squadron, took over the mission, personnel and equipment of the 526th, which was simultaneously inactivated. While this action was almost tantamount to redesignation, it was not an official redesignation. One half of the squadron's aircraft were maintained on fifteen minute alert, fully fueled and ready for combat to reduce vulnerability to a Soviet missile strike. in addition, the squadron periodically flew Operation Chrome Dome missions for "airborne alert training." The squadron trained for strategic bombardment to meet SAC commitments. Although the squadron did not deploy to support Operation Arc Light and Operation Linebacker, from 1968 to the end of the Vietnam War squadron crews deployed to the Pacific, where they flew B-52s of other units on combat missions. In 1980, two 644th Bomb Squadron crews (S-21 and S-31) received the Mackay Trophy for "executing a nonstop, around-the-world mission with the immediate objective of locating and photographing elements of the Soviet Navy operating in the Persian Gulf. With the end of the Cold War, its bombers were taken off alert. The squadron was inactivated in November 1994, as the 410th Bomb Wing became non-operational in preparation for the closure of K.I. Sawyer in 1995. Lineage Constituted as the 644th Bombardment Squadron (Light) on 16 June 1943 Activated on 1 July 1943 Redesignated 644th Bombardment Squadron, Light in 1944 Inactivated on 7 November 1945 Redesignated 644th Strategic Missile Squadron (IRBM-Thor) on 1 December 1958 Activated on 15 January 1959