Piercing the Fog - Air Force Historical Studies Office

Piercing the Fog
Y intelligence contributed as well to the detailed enemy reaction reports
Eighth Air Force A-2 and A-3 prepared jointly after each mission. The
purposes of these studies were to determine what aspects of an operation had
been conducted smoothly, identify problem areas, spot trends in enemy
defenses, analyze enemy tactics, and assess the probable benefits of different
defensive formations. To assist in report preparation, RAF Canterbury
forwarded to Eighth Air Force a detailed analysis, known as the Canterbury
Digest, of SIGINT acquired during each mission. In addition, Air Ministry
Intelligence (A.I.4) prepared and forwarded to the Americans longer term
studies on the GAF’s OB, tactics, and radio identification methods and
procedure^.'^'
Y intercepts contributed to the enemy reaction studies in several ways. By
monitoring aircraft transmissions, they provided comments on the enemy’s
running assessment of the course of the air battle and, more importantly, offered
insight into German aerial tactics. By identifying the German fighter control
locations, Y contributed to the picture of the enemy’s air defense organization
and areas of responsibilities. By linking call signs with the times and places that
the enemy aircraft checked in with ground fighter controllers, SIGINT enabled
Allied intelligence to determine more accurately the most likely locations of
primary fighter bases and the probable zones of concentrated attack.
By listening to initial German warnings of incoming American raids,
SIGN operators could determine the range of enemy radar equipment,
especially since ground controllers often indicated which site provided
information. Occasionally, SIGINT could pick up intelligence on the results of
American strikes against enemy airdromes. When a ground controller advised
a fighter he could not return to his normal base because of damage, Allied
intelligence knew they had damaged that field; it also confirmed which units
were stationed there. Directives to defensive interceptors low on fuel to land at
secondary recovery bases sometimes allowed operators to identify previously
unknown fields. The enemy also revealed flak locations in his transmissions.
Such revelations came either in the form of the identification of specific
locations to fighters or, more frequently, instructions to break off attacks at a
certain point. Radio interceptions helped to confirm the downing of enemy
fighters by aerial gunners and sometimes revealed the fate of friendly bombers
that had dropped behind the main force.”’
The information thus provided influenced both bomber and fighter
operations. With regard to bomber operations, Y intelligence was more valuable
in operational planning than in targeting. The insights it provided rarely affected
decisions on which targets to attack. Brig. Gen. Hams B. Hull, Eaker’s A-2 in
Eighth Air Force, recalled that they basically knew where the targets were in
those days. If the weather and available force permitted, Hull remarked that
“you were gonna go” regardless of the locations of defensive fighter force^.'^'
Y intelligence’s role was to assist the operational mission planners to determine
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