Archie to SAM: A Short Operational History of Ground-Based Air ...

AIRMEN VERSUS GUERRILLAS
2,000 guns within six months. In 1967, Pacific Air Forces estimated
that there were 9,000 antiaircraft weapons in North
Vietnam, while a Headquarters Air Force estimate put the number
at 3,100 medium (37 mm or 57 mm) and 1,300 heavy (85
mm or 100 mm) guns. With better intelligence, the estimate
was lowered to 2,000 guns by the end of 1969 and to less than
1,000 guns (37 mm and larger) in 1972. Whatever their numbers,
their impact was significant. 12
The farther north the Airmen operated, the more intense were
the defenses. Although only 20 percent of US sorties over Indochina
in 1965 were against North Vietnam, 62 percent of its
combat losses were there. The following year, 1966, proved only
a little better, with about 30 percent of the total Indochina sorties
and fewer than 60 percent of losses occurring over the north.
The area north of 20 degrees latitude, especially around the
Hanoi-Haiphong area, proved most dangerous. In the period
September 1966 through July 1967, the United States flew fewer
than 30 percent of its North Vietnam attack sorties north of 20
degrees yet lost 63.5 percent of its aircraft in that area. 13
In all, the United States lost just over 2,400 fixed-wing aircraft
in flight to enemy defenses during the Vietnam War
(through 15 August 1973). Of the known causes of loss, gunfire
caused 89 percent; SAMs, 8 percent; and MiGs, 3 percent.
In addition, the United States lost approximately 2,400 helicopters
in flight to enemy action, all but nine (two to MiGs and
seven to SAMs) to AAA (fig. 56). The Communists downed about
1,100 American planes over North Vietnam, 72 percent to
gunfire, 19 percent to SAMs, and 8 percent to MiGs. 14
The American Airmen initially used nuclear delivery tactics
that they had practiced in the late 1950s and early 1960s:
high-speed, low-altitude approaches and a rapid climb (popup)
to bombing altitude just before reaching the target. One
adjustment with conventional ordnance was to make multiple
passes over the target, but intense ground fire and the resulting
losses forced a change. Therefore, the Airmen raised approach
altitudes to 15,000 to 20,000 feet, from which the aircraft
dive-bombed their targets and limited attacks to a single
pass. This reduced losses, but, as a consequence, it also reduced
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