same month. On the morning of 27 October, a SAC RB-47H of the 55th Strategic Reconnaissance Wing, forward deployed to Kindley AFB, Bermuda crashed on takeoff, killing all four crewmembers, while later that afternoon, a 4028th Strategic Reconnaissance Squadron U-2 forward deployed to McCoy AFB for BRASS KNOB operations was shot down over Cuba by an SA-2 Guideline missile, killing the pilot, Major Rudolf Anderson. Throughout the early 1960s, the Kennedy Administration, under the aegis of Secretary of Defense McNamara, cancelled numerous SAC modernization programs. This included the Mach 3 North American B-70 Valkyrie in 1961, the GAM-87 Skybolt missile in 1962, and the Rocky Mountain Deep Underground Support Center in 1963. The B-70's demise came due to its design as a high-altitude bomber with very limited low-altitude performance, making it vulnerable to rapid advances in Soviet high altitude surface-to-air missile defense systems. The following year, Skybolt, an air-launched ballistic missile, was cancelled following numerous test failures and the perceived greater reliability of land-based and submarine-based ballistic missile systems. Although initially entering service in 1957, SAC's 2nd-generation aerial refueling aircraft, the KC-135 Stratotanker, had reached sufficient inventory numbers to allow SAC to begin divestiture of its KC-97 Stratofreighter tankers, transferring them to SAC-gained Air Force Reserve and Air National Guard units. As the KC-135 became the primary aerial tanker in active service, SAC employed the aircraft for several non-stop B-52 and KC-135 flights around the world, demonstrating that SAC no longer needed to depend on Reflex stations at air bases in Spain and Britain.) Vietnam War and latter half of the Cold War SAC's air war in Vietnam After the Secretary of Defense rejected LeMay's November 1964 proposal for a "...strategic air campaign against 94 targets in North Vietnam...", thirty SAC B-52Fs were deployed to Andersen AFB, Guam on 17 February 1965, representing the first increment of SAC aircraft forward deployed for the Vietnam War. The following month, in March 1965, the Strategic Air Command Advanced Echelon (SACADVON) was established as a "...liaison unit for CINCSAC [was] located at MACV Headquarters to assist with the B-52 effort." On 23 May 1965, SAC B-52Fs began unarmed missions for radar mapping "...and later to test bombing with the assistance of ground homing beacons..." SAC began saturation bombing on 18 June 1965 (8000 tons per month in 1966) and conducted Operation Arc Light missions from 1965 until the end of hostilities involving U.S.