Table Of ContentUnited States Cryptologic History
A Priceless Advantage
U.S. Navy Communications Intelligence
and the Battles of Coral Sea,
Midway, and the Aleutians
series IV: World War II | Volume 5 | 2017
Center for Cryptologic History
Frederick D. Parker retired from NSA in 1984 after thirty-two years of service. Following his
retirement, he worked as a reemployed annuitant and volunteer in the Center for Cryptologic History.
Mr. Parker served in the U.S. Marine Corps from 1943 to 1945 and from 1950 to 1952. He holds a
B.S. from the Georgetown University School of Foreign Service.
This publication presents a historical perspective for informational and educational purposes, is the result
of independent research, and does not necessarily reflect a position of NSA/CSS or any other U.S. govern-
ment entity.
This publication is distributed free by the National Security Agency. If you would like additional copies,
please email [email protected] or write to:
Center for Cryptologic History
National Security Agency
9800 Savage Road, Suite 6886
Fort George G. Meade, MD 20755
Cover: (l to r) Admiral Isoroku Yamamoto, Commander in Chief, Japanese Combined Fleet, 1942; aircraft
preparing for launch on the USS Enterprise during the Battle of Midway on 4 June 1942 with the USS
Pensacola and a destroyer in distance; and Admiral Chester W. Nimitz, Commander in Chief, Pacific
Fleet, ca. 1942-1944
A Priceless Advantage:
U.S. Navy Communications Intelligence
and the Battles of Coral Sea,
Midway, and the Aleutians
Frederick D. Parker
Center for Cryptologic History
National Security Agency
Reissued 2017 with a new introduction
First edition published 1993. Second edition 2011.
A Priceless Advantage
Contents
Introduction to 2017 Edition
by John A. Tokar ........................................................................................................................................v
Historian’s Introduction to 2011 Edition
by David A. Hatch ...................................................................................................................................vii
Foreword to 1993 Edition
by Henry F. Schorreck ..............................................................................................................................ix
Introduction ...........................................................................................................................................1
Part One: The Battle of the Coral Sea
Japanese Strategy ..................................................................................................................................3
American Countermeasures ..................................................................................................................5
Japanese Preparations for Moresby........................................................................................................8
Naval COMINT Centers and Their Reports on Japanese Preparations for the Invasion of
Port Moresby, Fiji, Samoa, and New Caledonia ..........................................................................10
Melbourne ........................................................................................................................................11
Hawaii (Hypo) ...................................................................................................................................12
OP-20-G Washington/Negat ............................................................................................................16
Communications Intelligence and Japanese Intentions toward Port Moresby ....................................17
The Battle Begins ..............................................................................................................................26
Overview ...........................................................................................................................................27
The Land Route to Port Moresby ......................................................................................................29
Notes .................................................................................................................................................30
Part Two: The Battles for Midway and the Aleutians
Japanese Strategy ...............................................................................................................................35
Japanese Preparations ........................................................................................................................36
COMINT Reflections of Japanese Preparations for Midway and the Aleutians ..................................38
The Battles Begin ..............................................................................................................................54
Conclusions .......................................................................................................................................60
Epilogue .............................................................................................................................................62
Notes .................................................................................................................................................67
Bibliography .......................................................................................................................................73
A Priceless Advantage
Introduction to 2017 Edition
Th e Center for Cryptologic History is pleased tologic efforts paid obvious rewards with respect
to reissue one of its earliest works, Fred Parker’s to the outcome at Midway, Mr. Parker also pays
1993 study, A Priceless Advantage: U.S. Navy Com- particular homage to how groundbreaking this
munications Intelligence and the Battles of Coral Sea, work was in the months preceding the Coral Sea
Midway, and the Aleutians, to commemorate the engagement. Furthermore, his treatment of the
75th anniversary of these important World War II attack on the Aleutian Islands, often neglected, is
battles. Th is is the second time that CCH has cho- fascinating.
sen to reprint it, the last being in 2011. While the
Did communications intelligence provide
layout and design of the previous edition were in
the margin of victory at Midway and, to a lesser
need of a refresh, Mr. Parker’s research and writing
extent, Coral Sea? The sailors, marines, and avi-
stand the test of time.
ators who risked their lives in May and June of
Few will argue with the seminal importance of 1942 certainly deserve the bulk of the acclaim.
the outcome of the Battle of Midway, not only on However, the decryption of the Japanese Impe-
the war in the Pacific, but ultimately on America’s rial Navy codes and subsequent analysis by Joe
role in the world. After June 1942, Japan would Rochefort and others enabled Nimitz to decisively
never again be on the strategic offensive in the position his forces to attack Yamamoto’s carriers.
Pacific, even though three bloody years of fight- Armed with solid estimates of the size, direction,
ing would ensue. After ultimate victory in World and attack date of the enemy force, Nimitz not
War II, the United States could no longer enter- only had confidence in how and where to deploy
tain notions of isolationism and was thrust into a his ships, he was able to argue against the alterna-
leadership role which we have never yielded. The tives being proposed by some in Washington. We
long-term repercussions of these relatively brief remain indebted to Mr. Parker for this powerful
moments of history are undeniable. contribution to cryptologic history.
As NSA Historians Henry Shorreck and David Others have since built upon this very solid
Hatch have noted in the previous introductions to foundation, but Mr. Parker was one of the earli-
this work, Mr. Parker’s real talent was his ability to est historians to compile such a complete picture
connect the far-flung cryptologic threads leading of communications intelligence in the Pacific.
to Coral Sea and Midway in a way that had not For those seeking additional study, consider Mr.
been done earlier. Prior to this work, World War Parker’s Pearl Harbor Revisited: United States Navy
II histories, when they talked about cryptology at Communications Intelligence, 1924-1941, also
all, tended to focus upon its impact to a particular available from CCH, and Elliot Carlson’s book,
battle or event. Mr. Parker’s monograph brilliantly Joe Rochefort’s War: The Odyssey of the Codebreaker
paints a picture of the meticulous work performed Who Outwitted Yamamoto at Midway.
by cryptologists in Hawaii, Washington, DC, and
John A. Tokar
elsewhere, and how they provided Admiral Nimitz
Chief, Center for Cryptologic History
with this “priceless advantage.” While these cryp-
v v
A Priceless Advantage
vi
A Priceless Advantage
Historian’s Introduction to 2011 Edition
Fred Parker’s 1993 study of the early World This is what makes Mr. Parker’s book of last-
War II battles of Coral Sea, Midway, and the Aleu- ing value. Along with the story of how cryptol-
tians, A Priceless Advantage, was one of the earlier ogy served the nation well in a period of crisis, he
books published by the Center for Cryptologic details how communications intelligence was pro-
History. It was, in fact, a companion piece to Mr. duced, and how it grew through the experience of
Parker’s Pearl Harbor Revisited. those who supported the war fighters.
As then-historian Henry Schorreck pointed Mr. Parker also adds a clear exposition of the
out in his original introduction to the mono- case of journalist Stanley Johnston, a story that is
graph, many historians of the time tended to still controversial in some circles.
focus on the cryptologic contribution in partic-
Unfortunately, contrary to what Mr. Schor-
ular battles. Mr. Parker’s insight, however, was to
reck hinted in his original introduction, Mr.
show the continuity of cryptologic enterprises in
Parker was unable to complete any additional
all three battles—and beyond—as well as the con-
studies of the war in the Pacific while with the
tinuity of cryptologic operations from the prewar
CCH. But his two completed studies add signifi-
efforts to the more mature work done at the time
cantly to our understanding of a vital tool in the
of Midway.
service of our nation, one that did indeed give a
Unfortunately, the weakness Mr. Schorreck “priceless advantage.”
saw in the early books on wartime cryptology still
For those who wish additional reading on
obtains. While a few good studies on the growth
related subjects, I would recommend Mr. Parker’s
and practice of cryptology in the 1940s now exist,
other book, mentioned above, and Robert L. Ben-
the tendency of authors on military subjects has
son’s A History of U.S. Communications Intelligence
been—and, all too often, still is—to deal only
during World War II: Policy and Administration.
with the effect of decrypts on this or that partic-
Both volumes are available from the Center for
ular battle or decision. It sometimes seems as if
Cryptologic History.
decrypts dropped from above like manna.
David A. Hatch
NSA Historian
vii vii
A Priceless Advantage
viii
