Piercing the Fog - Air Force Historical Studies Office

The European Theater of Operations
closest . . . coordination of ‘U,’ ‘Y,’ and Photo Recce sources was necessary. .
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British and American flyers photographed daily, sometimes twice a day,
airfields on Sicily and Italy, with the results of their efforts used to confirm
information acquired by ULTRA or Y. For example, while ULTRA picked up the
order for GAF units to withdraw from Sicily and move up the lower part of Italy
under pressure of Allied air strikes, it was the Y-Service that tracked virtually
every aircraft movement. This information guided photoreconnaissance
missions that, by confirming the arrival of enemy units at rear bases, provided
the information necessary to direct attacks on these installations.“ Y-Service
intercepts discovered at least one airfield.
Of particular importance for operational planning was the analysis
intelligence provided on the enemy’s air defense systems. Information on the
German radar network and flak defenses came from aircraft called ferrets
designed to carry equipment analyze radar capabilities. The AAF’s first ferret
aircraft in the Mediterranean were B-17s modified to be electronic intelligence
collection aircraft, as based on extensive work being done at the Naval Research
Laboratory in Washington, D.C., and at the AAF’s Aircraft Radio Laboratory
at Wright Field, Ohio. By the fall of 1943, three such aircraft were on station in
the region. Each carried directional antennas and a series of receiver sets that
allowed it to monitor the frequencies used by a variety of German early warning
and gun control radars. With this equipment, the aircrews could plot thelocation
of radars associated with enemy air defenses. The intelligence staff also used the
results of Y-Service monitoring of radio transmissions, of pilot debriefings, and
of photointerpretation? By June 1943, according to the chief Y officer, the
Allies were “fully conversant with all the activities of the enemy’s early
warning system, its extent and efficiency, and the strength and location of any
opposition likely to be encountered. . . .”lo This knowledge allowed intelligence
to recommend to operations the best routes to and from targets to avoid enemy
defenses. It was also used to knock out elements of that defensive system,
including AA batteries and fighters as well as radar. It also allowed for effective
jamming on the proper frequencies, while concurrent Y intercepts indicated the
success of such jamming.”
Even allowing for the fact that the Germans by this point in the war
considered the Mediterranean a secondary war front, the wide-ranging Allied
knowledge of Axis air operations and air defenses was remarkable. This
understanding allowed a range of military options that theAllies could use to
their distinct advantage. The influence of intelligence on planning could clearly
be seen as HUSKY drew near. Between June 15 and July 7, 1943, Allied air
forces conducted fourteen different raids against portions of the German air
defense network. As a result of these attacks, Colonel McDonald concluded in
his after-action report, “The enemy’s radar defenses in Sicily were crippled to
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