Historical Dictionary of United States-Japan ... - Bakumatsu Films

172 • MAGIC
MAGIC. MAGIC was the name given to the code-breaking device that
allowed American officials after 25 September 1940 to read Japanese
diplomatic traffic. The intercepted and decoded messages—which by
late 1941 numbered between 50 and 75 messages a day—were immediately
made available to President Franklin D. Roosevelt, his
secretaries of state, war, and the navy, and a select group of other officials.
The question inevitably arises: Did the Roosevelt administration
use these decoded messages judiciously? From the vantage point of
hindsight, it might be answered in the negative. To cite but one example,
MAGIC in early July 1941 alerted the Roosevelt administration
to Japan’s decision to occupy southern Indochina. After various
warnings and a proposal for the neutralization of Indochina were ignored
by Tokyo, a presidential order froze Japanese assets in the
United States on 25 July. This may have had the unfortunate effect of
convincing the Japanese army and navy leadership—who had not
foreseen such a sharp reprisal—that they now had nothing to lose. On
28 July, 40,000 Japanese troops marched “peacefully” into southern
Indochina. In short, there was no compelling reason to freeze Japanese
assets before the occupation of southern Indochina had taken
place. In this way, MAGIC may have had the unfortunate effect of
nullifying the admittedly slim chances of a diplomatic breakthrough
on the issue of Indochina.
In light of revisionist charges to the effect that Roosevelt maneuvered
the Japanese into firing the first shot—and, in particular, the
charge that he was aware of Japanese plans to attack Pearl Harbor—
it is necessary to recall that Magic did not enable Washington to read
Japanese army or navy plans. As one authority has noted, though
Washington by late November 1941 had come to expect war with
Japan, that expectation did not imply knowledge of an attack on Pearl
Harbor. See also PACIFIC WAR; WORLD WAR II.
MAHAN, ALFRED THAYER (1840–1914). After service as an officer
in the U.S. Navy, Mahan became a lecturer on naval affairs and
president of Newport War College. His book, The Influence of
Seapower Upon History, first published in 1890, was an influential
work around the world, including in Japan, which was then building
its modern navy. See also AKIYAMA, SANEYUKI.