the mid-1970s, the original AC Delco inertial guidance system had become obsolete and spare parts could no longer be obtained for it, so the guidance packages in the stock of Titan missiles were replaced by the Universal Space Guidance System. After the two accidents in 1978 and 1980, respectively, deactivation of the Titan II ICBM system finally began in July 1982. The last Titan II missile, located at Silo 373-8 near Judsonia, Arkansas, was deactivated on 5 May 1987. With their warheads removed, the deactivated missiles were initially placed in storage at Davis–Monthan Air Force Base, Arizona, and the former Norton Air Force Base, California, but were later broken up for salvage by 2009. A single Titan II complex belonging to the former strategic missile wing at Davis–Monthan Air Force Base escaped destruction after decommissioning and is open to the public as the Titan Missile Museum at Sahuarita, Arizona. The missile resting in the silo is a real Titan II, but was a training missile and never contained fuel, oxidizer, or a warhead. Number of Titan II missiles in service, by year: 1963: 56 1964: 59 1965: 59 1966: 60 1967: 63 1968: 59 (3 deactivated at Vandenberg Air Force Base) 1969: 60 1970: 57 (3 more deactivated at Vandenberg Air Force Base) 1971: 58 1972: 57 1973: 57 1974: 57 1975: 57 1976: 58 1977: 57 1978: 57 1979: 57 1980: 56 1981: 56 (President Ronald Reagan announces retirement of Titan II systems) 1983: 53 1984: 43 (Davis–Monthan Air Force Base site closure completed) 1985: 21 1986: 9 (Little Rock Air Force Base closure completed in 1987) Operational units Each Titan II ICBM wing was equipped with eighteen missiles; nine per squadron with one each at dispersed launch silos in the general area of the assigned base. See squadron article for geographic locations and other information about the assigned launch sites. A real Alert Real Response AAFM September 1999 308th Strategic Missile Wing 1 April 1962 – 18 August 1987 Little Rock Air Force Base, Arkansas 373d Strategic Missile Squadron 374th Strategic Missile Squadron 308th Missile Inspection and Maintenance Squadron 381st Strategic Missile Wing 1 March 1962 – 8 August 1986 McConnell Air Force Base, Kansas 532d Strategic Missile Squadron 533d Strategic Missile Squadron 390th Strategic Missile Wing 1 January 1962 – 31 July 1984 Davis–Monthan Air Force Base, Arizona 570th Strategic Missile Squadron 571st Strategic Missile Squadron 1st