Piercing the Fog - Air Force Historical Studies Office

Tools of Air Intelligence
The results of the Navy’s efforts to penetrate Japanese naval ciphers were
the information on Japanese intentions that led to the standoff in the Coral Sea,
blocking Japan’s advance on Port Moresby and ensuring the victory at Midway,
which crippled Japan’s carrier operations. In March 1943, the Army opened the
Wireless Experimental Center in New Delhi-a cooperative effort with the
British ULTRA operation. Code breakers there soon broke a Japanese military
code-the water transport code.188 As a result, throughout the remainder of the
war SIGINT contributed to attacks on critical Japanese shipping, initially
through monitoring of actual shipping schedules and eventually through
directing specific attacks by American submarines.’” An example of this
occurred in April 1944 when analysts learned of a major Japanese resupply
convoy of 9 merchant vessels and 12 escorts moving from Chinese ports to
Hollandia bases with over 20,000 troops and supplies. American naval
submarines sank at least 4 of these vessels with a loss of over 4,000 troops.1w
B Section
By mid- 1943, determined that SIS continue in breaking a fairly representative
flow of Japanese military ciphers and having obtained sufficient manpower to
conduct a comprehensive analytical program, Colonel McCormack established
a section dedicated to studying Japanese military messages and disseminating
the results-the B Section.’” Initial efforts by the new organization proved
frustrating as the code breakers encountered a bewildering array of codes being
used by the Japanese services, often with only fragmentary intercepts. They
lacked background data; as the official history notes, there were “difficulties of
translation and possibilities of erroneous interpretation. . . . It had become
evident that the potential of intelligence to be derived from Japanese military
traffic could be derived only by employing a very large number of personnel of
the highest quality.” Addressing the need for qualified analysts, in early January
1944 McCormack agreed to an authorized strength in B Section of 280 officers
and 120 enlisted members. Recruiting proved difficult, and by the middle of that
year the Army had assigned only 79 officers and 65 enlisted.’’’
Though few in number, the air members of the new section began from its
inception to accumulate information about the Japanese Army Air Force. Using
AAF officers trained at the AAF’s air intelligence school as well as other flying
officers, this OB section became the primary source of intelligence on the
organization of the Japanese Army Air Force by March 1944.Iy3 From message
intercepts, B Section constructed a detailed air OB as well as unit dispositions
and strength estimates. In April 1944, section members began to prepare weekly
estimates of Japanese air strength that were issued separately from the MAGIC
Diplomatic Summaries and other analytical products. These reports were part
of the larger Japanese Order of Battle Bulletins that also began to appear in
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