Activation of new aaa units - Air Defense Artillery

1948 AAA DEFENSE OF WASHINGTON 13
PEIIC£NT....&E OCCUR"I!NN
JANUAt'r Q.'~",,,,,VAL MEANS
337.: 20,000 -ft. CA p" HA'TT1f''''S N.C
Figure 5-Winds Aloft Percentage Occurrence by Direction.
150° and 120°; Battery T, the flak tower, alo~g 240° and
270°; Battery V of 12 guns along 120° and 90°; and Battery
MM of 10 guns along 0° and 30°. One reason for the
top priority of approach of course 180° is that only Battery
1, and possibly D, produce a major effect along this course;
although A, B, E, F, G, J, K, T, U, V, X, Y, and HH all
bear along some part of the approach.
EFFECT OF GUN POSITION
All flak analysis computers show that there is a wide
variation in the all-around effectiveness of a batterv as a
function of its position, or distance from the target' being
attacked. A study was made of position vs. effectiveness, the
results being plotted in Figure 4. Batteries U, Y, X, HH, T
and GG, that is, those closest to the target, have the greatest
summation of effectiveness along the twelve cardinal
courses.After the bomb release line is passed the effectivenessper
gun drops off rapidly until at the start of the bombing
run, BRL-60, the effectiveness has dropped to onlv
one-third of its maximum value. This would indicate th;t
the maximum number of guns should be placed about 3000
yardsinside the bomb release line for each individual target.
It is recognized that the Hamburg defense was constructed
for an initial bomb release line of 6500 vards outside the
defended zone. It is believed that a better 'BRL would have
been a composite circle made up of the BRL's from the
three top priority targets in the area. Certainly the defense
should have been as centralized as possible with more batteriesin
or near the defended zone."'"(See footnote p. 14.)
The above conclusion is somewhat at variance with
American antiaircraft tactical thinking. This thinking
should be modernized by adopting the methods of flak
analvsis to the studv of the effectiveness of a defense. Flak
~omputers should be used to analyze our tactical thinking
III order to increase the destructive fire of batteries.
In follmving the theory of mutually supporting distance
~vefall into the error of reducing our defenses as the targer
ISapproached. For example, assume that five batteries were
placed on the BRL of radius 4500 yards, this giving a mutually
supporting distance bef:\\'een batteries of 5280 yards...
If then another ring of batteries were constructed at a radius
of 9000 yards it would require 10.6 or II batteries i.fiordef
to maintain the same mutually supporting distance. A much
better solution, according to the results obtained from flak
analysis, ~ould be to divide the defense, eight batteries in
both the mner and the outer ring. If we must bow to the
g~ of mutually-su'pporting-distance then the eight battenes
of the outer rmg could be pulled in until this condition
is satisfied: and .the inner ring pulled in accordingly.
~e~an poh~y WIthregard to the defense of single small
ObjectIvesreqUIred an absolute minimum of six batteries,
with eight preferred. Our teaching has always emphasized
the "too few,"-our shooting is not that much better than
that of the Germans.
PREVAILING \\1INDS ALOFT
~ne of.the a.rguments ag~inst including the effect of pre-
~aIlmg wmds m the planmng of the dispositions of guns
m any defense has been that there is no persistency in the
prevailing winds over our major cities. This is definitely a
false assumption. Data has just been secmed on the winds
at 6000, 7000 and 8000 meters over Cape Hatteras, N. C.
This shows that there is a seasonal variation in the winds
aloft, but that particularly during the six months from November
through April there is a definit.~persistency. The
results for January 1946-47-48 are shown in Figure 5, indicating
that 92% of the winds aloft are in the 45° sector
from W-WSW-SW. During July and October this drops
to 38%, but the annual mean for this sector is 63%. The
mean speed for this period was 37 miles per hour with
about 2% calms, and 1% winds over 100 miles per hour..
With such a persistency of wind over emr east coast, all
planning of antiaircraft defenses should include the effect
of winds aloft. This prevailing wind must be a cbnsideration
in tactical planning. Such a study could well be combined
with one on the value of auxili:lIY positions. The
commander of a defense could well have auxiliary positions
prepared for various directions of the wind, and then order
certain batteries into these auxiliary positions when the
winds aloft watranted the shift. In the meantime these
auxiliary positions should be maintained as dummv positions..
In the photo-interpretation of aerial photographs of
Kyushu and Honshu the Japanese did such an excellent
job of setting up dummy positions that it was difficult, if
not impossible, to distinguish them from the real positions.
Evaluation of the defenses therefore became inaccurate.
Camouflage in many cases can be detected by good photointerpreters
by comparison methods, \vhereas dummy positions
when properly constructed are difficult to detect.
LESSONS LEA&~ED FROM GERMAi.~ DEFENSE
The follo\\'ing lessons appear to be self-evident from the
aboye analysis of the Hamburg-\Vashington defense:
(a) If Hamburg was worth defending with 398 heavy
guns and Berlin with 785 guns, our previously planned defenses
of New York, \Yashington, Norfolk, Philadelphia,
Boston, and Bridgeport-to mention onlY a few kev cities
on the east coast-were far from adequ~te. CertaiIily 300
guns in a centripetal defense of \Yashington would have
heen a minimum. This \\'ould haye meant well over 1000
guns for the greater Xe\\' York area.
.' (b) A centripetal defense with many guns close to the
. target and the bomb release line is far superior to one "indepth-outward."