 The division's units assumed a heightened alert role during the Cuban Missile Crisis, including the first SAC LGM-30A Minuteman I to be put on alert.The division continued at Ellsworth until June 1971, when SAC organized its divisions on a weapons system basis, and its bombardment and missile wings were reassigned to different divisions.Starting in 1957, the 28th Bombardment Wing at Ellsworth Air Force Base began to upgrade from the Convair B-36 Peacemaker to the Boeing B-52 Stratofortress.