Piercing the Fog - Air Force Historical Studies Office

Tools of Air Intelligence
Part of this arrangement was the implicit agreement that, at least in the early
days of fighting, the Department of the Navy would be concerned with the
Pacific.
McCormack quickly realized that he needed to get important SIGINT in a
usable format and in a timely fashion to Washington's decision makers. He
decided to use a periodic intelligence summary based upon the latest MAGIC
intercepts integrated with previous MAGIC information. Started in March 1942
and initially called The MAGIC Summary, these reports quickly proved a distinct
improvement over the pre-Pearl Harbor practice, whereby the services merely
forwarded portions of intercepted messages with little or no analysis. By the end
of 1942, these summaries, having been redesignated The MAGIC Diplomatic
Summaries, were issued daily, integrating both diplomatic and military analysis
gleaned from other intelligence sources. The Secretaries of War and the Navy;
the Chief of Staff, US. Army; the Commander-in-Chief, U.S. Fleet; and the
Chief of Naval Operations and key staff officers of the service departments saw
the daily synopses. Although Arnold and his AC/AS, Intelligence saw the
MAGIC summaries, not until late 1943 or early 1944 did they receive ULTRA
access. A copy of the MAGIC summaries reached the White House map room,
and by late 1942 the President's naval aide was reading the digest to Roosevelt
during his daily physical therapy sessions. Presidential confidant Harry Hopkins
and senior military advisor Admiral William Leahy checked the summaries
each morning. During presidential absences from Washington, Roosevelt
received daily MAGIC information in the form of disguised intelligence
briefings. At least at the highest level, SIGINT based upon MAGIC was having
an impact.'"
The degree and significance of the impact of MAGIC on national war policy
remains difficult to assess, primarily because all copies of the MAGIC Summaries,
except the record copy, were destroyed by the recipient after reading, and
few of the key participants referred to them in diaries or correspondence.
Wartime security measures strictly forbade mentioning any linkage of signals
decryption and the source.1x3 It is likewise difficult to link the specifics of highlevel
decisions on strategic use of airpower in the Pacific to MAGIC. Most of
these decisions resulted from deliberations of the JCS or the war strategy of the
president and his advisors. Again, strict security provisions prohibited explicit
mention of MAGIC or ULTRA and its relationship to such decisions that appeared
in the JCS papers. MAGIC regularly provided Japanese attach6 reports from
places such as Hanoi and occupied China on the specific results of AAF
bombing attacks as well as long-term analysis of economic problems. To these
MAGIC assessments, air intelligence experts often added other SIGINT data and
their own analyses that stressed what impact the air campaign was having upon
future Japanese war-waging capabilitie~."~ Such firsthand bomb damage
assessments bolstered the AAF's demands for operations targeted on the seizure
of forward air bases. As these MAGIC reports were going directly to major
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