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The breaking of the
Purple cipher and
the brilliant entry,
before Midway, into
the Japanese naval
code were proof
enough that the
intellectual base of
American
cryptanalysis was
strong. Yet once the
nation was plunged
into war several
weaknesses were
immediately
apparent. Apparent,
indeed, from the
very day of the
Pearl Harbor attack
In spite of pre-war
recruitment and
farsighted training
there was still a
critical shortage of
personnel in all
areas of signal
intelligence.
Indeed, a revolution was necessary, as may be
gauged from the experience of a single lieutenant in the Signal Corps,
Howard W. Brown. During the summer of 1941 Brown was Operations Officer in
tie Army's little Sigint unit in the Philippines, which, headed by the able
Major Joe Sherr, consisted of no more than six sergeants, three corporals
and six privates. By an agreement between the Army and the Navy; reached at
a conference in Manila in May 1941, the Navy's own Sigint unit, Cast, was
concentrating (in its tunnel on Corregidor) on breaking Japanese diplomatic
traffic, since it alone possessed a Purple machine. Sherr's team did the
interception. What is astonishing is the slowness-and therefore the
inefficiency-of the routine as Howard's own account (in his "Reminiscences
of Lieutenant Colonel Howard W. Brown*, prepared under the direction
of the Chief Signal Officer) reveals. He is describing the method for
passing over intercepted signals and their translations between his own unit
and Cast.
The normal procedure for handling exchange information was as
follows.- Major Sherr or I would take the sealed bag into Manila in time to meet the
harbor boat arriving from Corregidor at 1000; hand our bag to the code room at Fort
Santiago, Manila ( a large vault built in one of the old Spanish dungeons); open the bag
and extract the decoded messages; arrange decoded messages in a folder, by points of
origin, attaching any message from previous days which had bearing on, or reference to,
the current messages; take the folder to G-2 (or in his absence to his assistant),
and let him read the file; return to the code room and file the translations by point of
origin and date.
When Headquarters, United States Armed
Forces in the Far East, was established in July 1941, the above procedure was
altered in that the file was first taken to General Sutherland, Chief of Staff to General
MacArthur, and if it contained anything which he thought might be of interest to General
MacArthur (which it frequently did) he would ask us to take it in to the General. Some of
the General's off-the-record comments were classic.
From a security standpoint this system was
perfect . . . The serious drawback was the time delay. For instance, a message intercepted
on the first day would be sent to Corregidor on the second day and the translation
received from the Navy on the third day if in a readable system. Sundays and holidays
usually delayed delivery another day because the Navy usually took these days off.
And so the system
continued until the Japanese attacked. It may have been secure, but if it be considered as
a means of operating wartime one might be forgiven for judging that they did things
quicker in the days of the Pony Express.
During the weeks after the war began, Brown
strove hectically to improvise, from bits and pieces of the sparse equipment available,
means of interception which would enable him to listen in to radio traffic of the Japanese
Air Force. Though he could not translate what he heard, by identifying individual call
signs he could often calculate when a raid was imminent and warn a threatened
airfield-only to discover, too often, that in these early days the U.S. Air Force had a
blithe contempt for Sigint and disregarded his prophetic voice, with the result that
precious planes were destroyed on the ground. It was war on a do-it-yourself basis. Still,
he became so expert at predicting the appearance of the reconnaissance aircraft which
regularly visited Corregidor, and so won the confidence of the anti-aircraft gunners, that
"we were often able to tell them what 'Foto Joe' was up to, and at times could tell
them at what time, and from where, he was likely to appear. The AA batteries would load
and cock their guns, and pull the triggers as 'Foto Joe' came by trying to gain altitude.
This information and action accounted for about six planes.' Before the end, a capture of
Japanese code books on Bataan made it possible to set up a small radio intelligence office
in Malinta Tunnel on Corregidor which, with four receivers and the occasional use or a
naval direction finder, spent a profitable time monitoring the signal circuits of the
enemy's army and air units in the Philippines, providing early warning about in coming
raids, and even registering Japanese losses. "We were able to confirm 'probables,' or
reports of safe arrival, and the extent of damage, by such messages as: 'Ikamura is
landing in the water, looks like he won't be home,' or 'Taji landed at Nichols with one
motor burning.'"
On the day that MacArthur departed, leaving
General Wainwright to make the final stand, the general summoned Brown to his office
shortly before midnight, shook his hand and said, "I want to congratulate you,
Captain Hart tells me that you have discovered a system to solve Japanese messages. I am
proud of you, and want to thank you." But, unlike Wainwright, Brown too left the
Philippines. After an abortive attempt to establish an intercept station on Mindanao, on
April 14 he was flown off to Darwin in Australia, a passenger in a moribund B-17, one of
whose engines was dead while another was spouting oil, "When we landed, more than one
big strong man kissed the ground."
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