Piercing the Fog - Air Force Historical Studies Office

Tools of Air Intelligence
cryptographic technology in early 1941 and to the rapid development of
otherwise remarkably integrated Anglo-American intelligence operations and
organizations. During the first eighteen months, American military commanders
in Europe and their superiors in Washington received only limited distribution
of decrypted ULTRA and did not understand, except for a very few technical
experts like the cryptologist William F. Friedman* of the Army’s Signal
Intelligence Service, how the British handled the deciphering, distribution, or
analysis of this inte1ligen~e.l~ For strategic air operations over Europe as well
as during Operation TORCH and the subsequent struggle for North Africa, the
British maintained complete control over the interception, decryption,
evaluation, and distribution of Enigma-generated intelligence.
By the spring of 1943 the United States sought a greater role in SIGN activities in Europe. The British remained extremely reluctant to relinquish their
monopoly over the Axis codes and ciphers, in part because the United States
already had a blemished record when it came to keeping military secrets. Just
days before Pearl Harbor the isolationist Chicago Herald Tribune had published
the text of the War Department’s so-called Victory Program for the development
of American military capabilities necessary to defeat the Axis in the event
of war. The Tribune’s source for this document was almost certainly an officer
within the War Department. In addition, from the fall of 1941 to the summer of
1942 the Germans had broken the code used by the American military attache
in Cairo, and they used the information thus gained in operations against the
British in the Western Desert. By 1943, however, the Americans could offer an
important bargaining chip, after recently breaking several of the major Japanese
high-level military ~iphers.’~
Despite an obvious wariness on both sides, the two governments signed an
agreement on sharing information on May 17, 1943. According to this
document, the British would continue their efforts against the German and
Italian high-grade ciphers (ULTRA) as well as lower-grade signals and radio
traffic sent in the clear (unencoded).? The Americans would continue their
assault against Japanese military, air, naval, and diplomatic ciphers.16 The
partners agreed to continue exchanging intelligence so gained and to establish
special procedures to ensure its secure handling and to prevent it from being
inadvertently commingled with intelligence from other sources. These
*William F. Friedman (1891-1969), a cryptanalyst of great ability, began to
appear prominently in Army SIGINT during World War I. After the war, Friedman
worked as the Army’s chief cryptanalyst in a very small office directed more to
developing new codes and ciphers than to penetrating those of foreign powers. He
was instrumental in training Army officers in cryptography and cryptanalysis and
in leading the team that broke the PURPLE cipher.
tlow-grade and high-grade in this context refer to the complexity of
encipherment, not to the inherent value of the intelligence that might be derived
from intercepted signals.
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