Complex sentence: When Mather AFB closed in 1993 pursuant to the 1989 BRAC, the 940th returned to McClellan AFB from July 1993 until May 1998, when McClellan AFB was also closed pursuant to 1993 BRAC action.
Split into simpler sentences: When Mather AFB closed in 1993 pursuant to the 1989 BRAC. The 940th remained at McClellan AFB from July 1993 until May 1998, when McClellan AFB was also closed pursuant to 1993 BRAC action.