The Tet Offensive: Intelligence Failure in War 9781501713361

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The Tet Offensive

A volume in the series CORNELL STUDIES IN SECURITY AFFAIRS

edited by Robert J. Art, Robert Jervis, and Stephen M. Walt A fulllist of titles in the series appears at the end of the book.

The Tet Offensive INTELLIGENCE FAILURE IN WAR

JAMES J. WIRTZ

CorneIl University Press ITHACA AND LONDON

Copyright © 1991 by Comell University All rights reserved. Except for brief quotations in a review,this book, or parts thereof, must not be reproduced in any form without permission in writing from the publisher. For information, address Cornell University Press, Sage House, 512 East State Street, Ithaca, New York 14850. First published 1991 by Comell University Press First printing, Comell Paperbacks, 1994 Printed in the United States 01 America Library of Congress Cataloging-in-Publication Data Wirtz, James J., 195&The Tet offensive: intelligence failure in war / James J. Wirtz. p. cm. - (Cornell studies in security affairs) Inc1udes bibliographical references and indexo ISBN 0-8014-8209-7 (pbk. : alk. paper) 1. Tet Offensive, 1968. 2. Vietnamese Conflict, 1961-1975Military intelligence. 3. Vietnamese Conflict, 1961-1975-United States. l. TIlle. ll. Series. DS559·8·M44W57 1991 959·704'38~c2o 91-55048 Cornell University Press strives to use environmentally responsible suppliers and materials to the lullest extent possible in the publishing oE its books. Such materials include vegetable-based, low-VOC inks and acid-free papers that are recycled, totally chlorine-free, or partly compased of nonwood Eibers. Paperback printing

10 9 8 7 6 5 4 3 2

Contents

AcknowIedgments Abbreviations

vii

ix

Introduction

1

PART 1.

2.

1:

"THE SIG VICTORY, THE GREAT TASK"

The Communist Debate over Strategy PIans, Preparations, and Objectives of the Tet Offensive PART

3. 4. 5. 6.

II: THE ORIGINS OF SURPRISE

The Sources of American Biases Missing the SignaIs: July-November 1967 Missing the Signals: December 1967-30 January 1968 Reacting to the Tet Offensive Conclusion: ExpIaining the Failure of Intelligence Bibliography Index

[v]

17 51

87

140

180

224

Acknowledgments

Many individuaIs and organizations have eased the task of preparing this manuscript. Robert Jervis, Richard Betts, Warner Schilling, Jack Snyder, and Robert Art not only provided comments that significantly improved the quality of this work but also served as fine exampies of how one approaches the discipline of political science. Jervis and Betts often went beyond the call of duty in providing both encouragement and help in securing the resources needed to undertake the project. I am indebted especially to Samuel P. Huntington, the John M. Olin Foundation, and the staff of the Center for International Affairs at Harvard University for providing the perfect research environment. By supplying funding for the 1985 and 1986 academic years and eight weeks of summer research, the Olin Foundation greatly facilitated the completion of this project. Sam Huntington de serves special praise for taking a keen interest in the pre-doctoral fellows at the CFIA and for creating a setting conducive to research and intellectual growth. While 1 was at the CFIA, Tom Fintel, Ira Klein, Timothy Lomperis, Douglas Macdonald, and Edward Rhodes were kind enough to read first drafts of many chapters; they caught several silly mistakes before they could cause me embarrassment. Even after the end of our days at the CFIA, Lomperis, Macdonald, and Rhodes continued to read chapters and to encourage me. Michael Handel and Richard Valcourt, who both share my interest in intelligence analysis, also provided encouragement and advice. Additionally, 1 thank George Allen, Walt Rostow, and Robert Ruhl Simmons for offering insights into several key events during the war. 1 al so benefited from Glenn Palmer' s comments on several chapters. 1 thank the Lyndon Baines Johnson Foundation for a grant that al[vii]

Acknowledgments

lowed me to use the documents maintained at the LB] Library in Austin, Texas. David Humphrey was a masterful guide to the materials on the Vietnam War maintained at the library. His help allowed me to compress months of research into a matter of weeks. Similarly, 1 am grateful to Stephen Eldridge of the Department of the Army, who guided me through the record s maintained by the Department of the Army and the National Archives. Both men showed extreme patience in the face of naive questions. As the manuscript reached its final stages, 1 benefited greatly from the computer support offered by Robert Friedrich. 1 thank Holly Baily, Patty Peltekos, and Kathleen Moschak at Cornell University Press for their assistance. They were kind to a first-time author, and their efforts greatly improved the manuscript. My parents, Charles John Wirtz and Elizabeth Goffa Wirtz, and my sister, Mary Elise Wirtz, deserve a special note of thanks since they continue to support me in my decision to pursue an academic career. By bearing more than their share of my financial and emotional burdens, my parents greatly eased the task of preparing this manuscript in its initial stages. Finally, 1 thank my wife, Janet Ayden Wirtz. Not only did she help me in a thousand different ways, she directly contributed to the completion of the work by painstakingly proofreading the manuscript. Her confidence in my abilities never wavered, and for this 1 am truly grateful.

Monterey, California

JAMES

J.

[viii]

WIRTZ

Abbreviations

ARVN Army of the Republic of (South] Vietnam CDEC Combined Document Exploitation Center (allies) CIA Central Intelligence Agency (U.S.) CICV Combined Intelligence Center, Vietnam (allies) CIDG civilian irregular defense group (allies) CINCPAC Commander in Chief, Pacific (U.S.) CMD Capital Military District (RVN) CMEC Combined Material Exploitation Center (allies) CMIC Combined Military Interrogation Center (allies) CMR Capital Military Region COMUSMACV Commander, U.S. Military Assistance Command, Vietnam CORDS Civilian Operations and Rural Development Support COSVN Central Office [Communist party] for South Vietnam CTZ corps tactical zone OlA Defense Intelligence Agency (U.S.) OMZ demilitarized zone FFV Field Force, Vietnam (U.S.) FWMAF Free WorId Military Assistance Forces (allies) GVN government of [South] Vietnam J-2 military intelligence staff JGS Joint General Staff (RVN) LOC lines of communication MACV Military Assistance Command, Vietnam MAF Marine Amphibious Force (U.S.) NV A North Víetnamese Army NIE National Intelligence Estímate (U.S.) NLF National Liberation Front NSA National Security Agency (U.S.) NVN North Vietnam PERINTREP Periodic lntl'lIigence Report (CICV)

[ix]

Abbreviations RVN RVNAF SAC SIGINT SVN USARV VC

People's Revolutionary party Rural Development (pacification] program (RVN) Republic of [South] Vietnam Republic of [South] Vietnam Armed Forces Strategic Air Command (U.S.) (electronic] signals intelligence South Vietnam U.S. Army, Vietnam Vietcong

VWP

Vietnamese Worker's (Communist] party

PRP

RD

VDRN

Viet-Nam Documents and Research Notes

[x]

The Tet Offensive

Introduction

On 31 January 1')68, during the Tet holiday, communist forces simultaneously attacked urban areas, military instaIlations, and government facilities throughout South Vietnam. By the time the offensive' s intensity began to wane on 13 February, 1100 Americans had been killed in action, and members of the Johnson administration and the American public had been stunned by the fury of the Tet aUacks. FoIlowing the offensive, the official U.5. government investigation into the circumstances surrounding the Tet aUacks concluded that, "although warning had ... been provided, the intensity, coordination, and timing of the enemy attack were not fully anticipated."1 U.5. and 50uth Vietnamese officers and intelligence analysts failed to anticipate the nature of the Tet offensive. This failure not only contributed to the initial military gains enjoyed by the communists but also increased the shock produced by the attack. Ultimately, it was the surprise, not the short-term military advantages, that reduced the willingness of the American pubJic and poJitical elite to continue to prosecute the war in Vietnam. 2 The Tet offensive was the decisive battle of the Vietnam War because of its profound impact on American attitudes about involvement in 50utheast Asia. In the aftermath of Tet, many Americans beca me disillusioned with the Johnson administration's conduct of the war. ro the American public and even to members of the adminIU.S. Congress, House Select Committee on Intelligence, U.S. Intel/igel1ce Age/lcies and Activities: Risks and Control o{ Foreig/l Intel/igence, 94th Cong., 1St sess. 1975, pt. 5, app.

4,1995· 2Headquarters, United Sta tes Military Assistance Command, Vietnam, Command History J968 (San Francisco, 1969), 1: 129; and George C. Herring, America's Longest War: The United States a/ld Vietnam, J950-J975 (New York, 1979), p. 188.

[1]

rile ld Offensive

istration, the offensive demonstrated that u.s. intervention in the ground war had produced a negligible effect on the will and capability of the Vietcong and North Vietnamese to continue in their struggle to unite Vietnam. The Tet offensive seemed to indicate to most observers that the three years of "big-unit war" that followed the deployment of U.S. ground forces in 1965 had produced only a steady stream of casualties on all sides. On the battlefield, Tet marked the turning point between U.S. escalation and withdrawal from the war. In the realm of domestic politics, the consequences of the offensive were al so profound. Tet discredited the Johnson administration, reinfordng the president's decision not to run for reelection. For many Americans, Tet enhanced the credibility gap between the electora te and government officials as battlefield developments apparently contradicted the claims of progress in the war made by the Johnson administration and the military. The offensive turned disengagement from the struggle in Vietnam into the American political priority for the next five years. Over the longer term, Tet marked the beginning of what Ronald Reagan called the "Vietnam syndrome": a period of public disillusionment with military intervention, defense spending, and an active anticommunist approach to foreign affairs. In a sen se, the Tet offensive quelled the crusading spirit that characterized America's postwar rush to intervene in conflicts in the Third World. Given the political impact of the Tet attacks, it would be logical to assume that the offensive dealt a devastating military setback to U.S. force s and their South Vietnamese allies. Dire consequences usually follow a disastrous defeat. Ironically, the allies defeated the communists dedsively during Tet. From the communist perspective, the offensive was a gamble, even a desperate gamble, taken to offset the overwhelming resources, mobility, firepower, technological sophistication, and professionalism of their opponent. The North Vietnamese and Vietcong hoped that the attacks would foster a revolt of the southern population against the government, thereby adding tens of thousands of combatants to the communist side. When the offensive failed to spark this insurrection, communist commanders lacked the resources needed to attain their ambitious objectives, and the alHes defeated their widely scattered forces piecemeal. Even though the Tet attacks failed to unfold as planned, the offensive eventually produced the outcome desired by the communists. The communists intended the surprise inflieted against the allies during Tet. They adopted a sophisticated strategy of deception, misleading their opponents about their intentions in a quest to elimina te or reduce the effectiveness of responses to the offensive. In wartime, [2]

Introduction

the active or passive effort to mislead, misinform, or confuse an opponent about one's capabilities or intentions can take several forms. A nation contemplating an attack can try to make its adversary locate its force s in the wrong place. In such instan ces, deceptive operations embody aH the signs of a real assault, to cause an opponent to believe that the pretended hostile activities are genuine. The Japanese aUack on the Aleutians on 3 June 1942, an effort to lure the U.S. Navy away from the Japanese forces that would conduct the planned amphibious landings on Midway, is an example of this type of operation. Deception during war also can be used to force an opponent to violate the principIe of economy of force. Such cases involve the attempt to cause the adversary to squander resources on nonexistent targets or in unimportant directions. During the Battle of Britain, for example, the British succeeded in channeling German air attacks away from actual facilities by constructing fake installations and by interfering with the Luftwaffe's electronic navigational aids. Cover, another type of deception, is intended to lull an opponent into a false sense of security so that one can seize the element of surprise. Here deception centers on the effort to disguise preparations for attack by convincing the opponent that genuinely hostile activities are harmless. Before Operation Barbarossa, the German invasion of the Soviet Union, the Nazis maintained normal diplomatic and economic relations with the Soviets in an ultimately successful effort to hide their preparations for invasion. Before Tet, the communists used a mix of active and passive deceptive strategies to mislead the allies about the location of the offensive and to hide preparations for the coming attacks. This strategy was insufficíent to secure military victory for the communists, but it did help to obtain the element of surprise. 3 If the cornrnunists failed to win the Tet offensive, what then ac-

counts for its effect on American perceptions of the war in Vietnam? Ultimately, the shock it produced was the catalyst that led to the reevaluation of u.s. policy. The Tet attacks failed on the battlefield, but U.S. forces did not anticípate fuHy the scope, intensity, targets, and timing of the offensive. The allies ~uffered a failure of intelligence during Tet, a failure that set the stage for changes in U.S. strategy. Why were the United States and its allies surprised by the Tet attacks? Intelligence analysts, soldiers, and political officials are gener3Charles Cruickshank, Deceptioll ill World War Il (Oxford, 1979), p. xi; Michael Handel, Military Deception in Peace alld War (Jerusalem, 1']8,), pp. 9-11; Gordon W. Prange, Mirac/e at Midway (New York, 1982), p. 116; Samuel Eliol Morison, History o[ United States Naval Operations in World War 11, vol. 4. Coral Sea, Midway alld SlIbmarillc Actions (Boslon, 1949), p. 77; and Barton Whaley, Codeword BARBAROSSA (Cambridge, Mass., 1973).

[3]

The Tet Offensive

ally surprised by their opponent's initiatives if they fail to accomplish four tasks, sometimes referred to as the "intelligence cycle": collection of information, analysis, response, and dissemination of warning. The first task is the collection of accurate information about the opponent's intentions and capabilities. There are, of course, a variety of ways to collect information about potentiaI adversaries, from simply reading the foreign press to using advanced technology to monitor the opponent's communications. Yet collection can be arduous because governments bent on surprising their opponents strive to prevent accurate information from reaching their victim. Even though the notion is tautological, surprise can occur because the victim lacks information about the opponent. In any event, one should not dismiss this most parsimonious explanation for a failure of intelligence without first demonstrating that information that could have warned the victim of what was about to unfold was available: It could be argued that, on balance, U.S. intelligence organizations enjoyed several advantages simply because they were already at war. Certain methods of collecting information obviously were not available; U.S. diplomats and journalists could not wander Hanoi listening for the latest rumor about the regime's intentions. But during war, events on the battlefield can produce an intima te, albeit sometimes painful, awareness of the opponent's idiosyncrasies and standard procedures. Other sources of information generally unavailable in peacetime-reconnaissance overflights, captured documents, and prisoner interrogations-also become available during hostilities. AIthough it was formidable, the task of collecting information before Tet was not insurmountable from the U.S. perspective. The second task, the analysis of evidence of enemy intentions and capabilities, is crucial, given the assumption that all information is inherently ambiguous. Current developments in widely scattered regions must be combined into a meaningful pattern. Past events must be linked to reports of future plans. Analysts also must differentiate between signals (accurate information about the enemy) and noise (inaccurate or irrelevant information) in attempting to predict the opponent' s moves. In devising estima tes, however, analysts are subjected to a variety of pressures. For example, the "cry wolf" syndrome, a set -- ·...., 'r . ~.--. "\ An Tu ......\.. c" An ~ . , ,. DlI1h . '\..,,,...c... ~. . 111 'y Giang