Foreign Relations of the United States Guide to Sources on Vietnam, 1969-1975
Prepared by Edward C. Keefer, John M. Carland, and Bradley L. Coleman
Office of the Historian, U.S. Department of State
Released February 1, 2012
The Vietnam war is one of the best documented events in U.S. history. Federal agencies generated a large and unique variety of archival material during the conflict, from traditional memoranda and telegrams, to backchannel messages and White House tape recordings. This guide to archival resources, based on the work of the Office of the Historian, U.S. Department of State, describes the sources used to compile the Foreign Relations of the United States (FRUS) documentary series on the Vietnam war during the Richard M. Nixon and Gerald R. Ford Administrations, from January 1969 to May 1975. Despite the expansive coverage dedicated to the Vietnam war in the Foreign Relations series, space constraints forced Department of State historians to choose carefully among the thousands of documents produced during the conflict. This guide aims to provide a road map for researchers seeking to go beyond documents included in Foreign Relations to archival resources housed both in Washington and in various locations around the country.
In compiling the Foreign Relations series, Department of State historians had a very specific mission to capture: the documentary record of high-level policy decisions and civilian direction and management of the war; U.S. political and military strategy; peace negotiations with the Democratic Republic of Vietnam (North Vietnam) and the National Liberation Front (NLF); U.S. support for the armed forces of the Republic of Vietnam (South Vietnam); and diplomatic, political, and economic relations with South Vietnam. The five Foreign Relations volumes covering the Nixon and Ford administrations contain notes on sources, annotated source lists, and copious footnotes. Readers should use this guide in conjunction with the published volumes. Before undertaking archival research, researches should study carefully the documentation contained in the Foreign Relations volumes on Vietnam from 1969 to 1975. Researchers can purchase the volumes through the U.S. Government Printing Office or view them free of charge on the Office of the Historian, U.S. Department of State website (history.state.gov). In keeping with prevailing scholarly practices, documents researchers initially encounter in the series should be cited to Foreign Relations.
During the Lyndon B. Johnson administration, the President directed that the U.S. military limit operations to South Vietnam, with the exception of the U.S. air campaign against the Ho Chi Minh Trail and the intermittent bombing of the North during Rolling Thunder. Department of State historians covering this period determined it desirable to segregate the conflicts in Vietnam, Laos, and Cambodia into separate Foreign Relations volumes. When Richard Nixon entered office in January 1969, however, the President and Special Assistant for National Security Henry Kissinger expanded the war beyond South Vietnam into enemy sanctuaries in Laos, Cambodia, and North Vietnam. For this reason, Foreign Relations volumes covering Vietnam during this phase of the war document events across Southeast Asia, including activities such as the invasions of Cambodia (1970) and Laos (1971); the widespread bombing of North Vietnam (1972); and the SS Mayaguez incident (1975).
After a careful reading of the Foreign Relations volumes, researchers should consult the extensive Presidential papers and other White House records at the Nixon Presidential Materials Project. In 2010 the Nixon records were transferred from the National Archives in College Park, Maryland to the Nixon Presidential Library in Yorba Linda, California. Within this collection, the most valuable information bearing on the administration’s management of the Vietnam War and its search for a negotiated peace in Southeast Asia are the National Security Council (NSC) Files.
Two sub-files within the NSC materials provide the best documentation: the Vietnam Subject Files and the Country Files for Vietnam. These files hold the working records of the NSC staff members responsible for analyzing information on Vietnam for Kissinger, who in turn would use their analyses in his communications with President Nixon. The Vietnam Subject Files is a topical collection that deals not only with Vietnam but also with Laos, Cambodia, Thailand, and Southeast Asia as a whole. For example, material on the 1971 U.S.-supported South Vietnamese cross-border operation, Lam Son 719, is in the Vietnam Subject Files under the sub-file Special Operations File. Although the Vietnam Subject Files collection is weighed towards military issues, it also contains abundant records on the attempt to manage the peace process in Vietnam after January 1973. Like other Nixon records, the archivists have prepared finding aids with folder titles. The Vietnam Country Files collection, consisting of 29 Hollinger boxes, holds diplomatic and political material primarily about Vietnam and U.S. relations with the Republic of Vietnam. The boxes, folders, and items within are organized chronologically. In some cases there are sub-chronologies in each folder of Department of State cables, intelligence cables, and memoranda. The Vietnam Country Files is the single most cited collection in the five Foreign Relations volumes on Vietnam from 1969 to 1975.
The Far East Country Files, 31 Hollinger boxes, contain folders on Cambodia, Laos, Southeast Asia, Indochina, and Thailand. Although similar in organization to the Vietnam Country Files, it lacks specific subject folders, but does include topical and issue-specific folders. Additionally, there is a Cambodian Operations File, consisting of 21 Hollinger boxes, that contains a combination of chronological and topical records covering the U.S.-South Vietnamese movement into Cambodia from April to July 1970. The files consist mostly of daily situation and action reports, including many to the President, as well as longer reports and briefings to Congress and others on the Cambodian operation. The Nodis/Khmer section of this file focuses on efforts by various nations to support the Cambodian effort.
The search for a negotiated peace is a principal theme of the Foreign Relations coverage of the Vietnam war. Official peace negotiations were held in Paris at the International Conference Center on Avenue Kléber. Documentation on these talks, consisting of some 28 Hollinger boxes, is located in the Paris/Talks Meeting Files. This file begins during the Johnson administration and contains the records—mostly cables to and from the delegation in Paris—of the W. Averell Harriman and Cyrus Vance Mission (HARVAN), from May 1968 to January 1969. During the Nixon administration, the file covers cable traffic between the Department of State and the delegation in Paris, and to and from the Embassy in Saigon. There are a few topical folders in the collection with non-telegraphic material, but it is essentially a cables file with the bulk of the material dated between 1969 and 1970.
The Nixon administration preferred to use private talks in Paris, as opposed to the official public sessions at Avenue Kléber, as the primary venue for serious negotiations. In August 1969, Washington and Hanoi opened a secret negotiations channel. At these discussions, Kissinger represented the United States and Hanoi’s Chief Delegate at Paris Xuan Thuy, later joined by Special Adviser Le Duc Tho, represented North Vietnam. Le Duc Tho was a member of the Politburo in Hanoi and the real chief of the delegation. The records of the Kissinger and Xuan Thuy-Le Duc Tho negotiations were maintained by NSC staff member Winston Lord, the principal note taker for these secret meetings, and are located in the NSC Files, For the President’s—China/Vietnam Negotiations, C.D. [Camp David]. This file includes virtually all verbatim memoranda of the secret talks, as well as summary memoranda prepared by Kissinger and his staff for the President. This collection also reveals how Ambassador Ellsworth Bunker and South Vietnamese President Thieu kept abreast of the negotiations. In all, the Vietnam negotiations portion of the file maintained by Winston Lord fills 24 Hollinger boxes. A second file by the same name exists in the NSC Files, and consists of 3 Hollinger boxes containing mostly copies of Kissinger’s secret talks with Le Duc Tho, original letters from Thieu to Nixon from late 1972 to early 1973, and memoranda of conversations for Kissinger’s trip to South Vietnam in October 1972 and Haig’s trip in November 1972.
As for U.S.-Soviet relations, the Nixon administration wanted Moscow to pressure North Vietnam into a political settlement. To this end, Nixon and Kissinger engaged in private talks with Soviet Ambassador Anatoly Fedorovich Dobrynin. Nine Hollinger boxes of records related to those meeting are in the NSC Files, President’s Trip File, Dobrynin/Kissinger.
Following the aforementioned collections, next in importance are several other collections within the NSC Files. The first is the Backchannel Files which contain secret communications between the White House (essentially the President or Kissinger) and U.S. ambassadors, conducted without the knowledge of the official Department of State bureaucracy. Although the collection includes all backchannel messages, a good portion relate to backchannel messages between the White House and Ambassadors Bunker and Graham A. Martin in Saigon, and to and from other ambassadors in Southeast Asia. For 1969, however, backchannel communications between the White House and Ambassador Bunker are filed in the Vietnam Subject File. On almost all occasions, these backchannel messages were more important to the policy process than the regular Department of State telegrams. Backchannel messages to and from U.S. negotiators in Paris are also in this collection.
The Kissinger Office Files—the records of the Special Assistant to the President for National Security Affairs maintained by his immediate staff—are also in the NSC Files. A key source for documents on U.S. policy toward Vietnam, this collection contains Kissinger’s trip files, items such as briefing books, memoranda, and memoranda of conversations relating to his travels. These records cover his visit to Saigon in October 1972 to confer with President Nguyen Van Thieu; his negotiating sessions in Paris with Le Duc Tho; his February 1973 Hanoi visit; and activities related to the June 1973 Joint Communiqué. The Kissinger Office Files also have separate Country Files, Far East, sub-section that contains records on Cambodia, especially relating to the efforts of Colonel Jonathan “Fred” Ladd, sent to Phnom Penh by the President, to bolster the fighting ability of Lon Nol’s armed forces. A Vietnam-South Vietnam Country File, which covers 1971–1972 and contains a sub-section on Vietnam-Vietnam Negotiations, are also in the Office Files but, it should be emphasized, the most important material on this issue is in the For the President’s Files.
Valuable documents relating to Vietnam are in other collections in the NSC Files. The Haig Chronological Files includes memoranda, correspondence, and message traffic to and from Haig, much of it relating to Vietnam. It also contains one box of transcripts of a number of telephone conversations among Haig, Nixon, Kissinger, and other NSC staff members. These transcripts do not seem to appear elsewhere and often contain significant policy discussions. The Haig Special File has material arranged topically, much of which relates to Haig’s trips to South Vietnam (aimed at informing President Thieu about the state of the negotiations and, more importantly, at persuading him to accept the American proposals and approach). This file also includes documents on Haig’s trips to other Southeast Asian nations. The Agency File, Department of Defense, contains considerable documentation on Vietnam, while the Subject Files (as opposed to the Vietnam Subject Files) hold only occasional Vietnam-related items, some of which is useful, such as Items to Discuss with the President. A chronological collection of documents within the NSC Files, the President’s Daily Briefing Files often include reports on Vietnam with handwritten comments by President Nixon. Finally, the Unfiled Material contains documentation on Vietnam. Made up of material not filed after the President resigned, the collection has no finding aid or organizational logic except that it is organized by date—earliest to latest. There is no easy way to review it except document by document.
The NSC Files in the Nixon Presidential Materials also contain the National Security Council Institutional Files (H-Files), which should not to be confused with the NSC Institutional Matters File (a sub-file of the NSC Files comprising 19 boxes). The H-Files, consisting of 315 boxes, until recently were under the control of the NSC but have now been transferred to the Nixon Presidential Library. These files contain the minutes of National Security Council Meetings and NSC subgroups such as the Review Group/Senior Review Group and the Washington Special Actions Group (WSAG), chaired by Kissinger and attended by deputy heads of the federal agencies and the Director of Central Intelligence. Furthermore, for each set of minutes there are corresponding folders containing papers Kissinger used to prepare for the meetings. For Vietnam and Southeast Asia, the WSAG functioned as the key policy and crisis management entity. It dealt, sometimes on a daily basis during critical periods, with events in Vietnam and Southeast Asia, making policy decisions, or asking the President to make the decisions, and following up on Presidential directives. In addition, this file hold records of the Vietnam Special Study Group (VSSG), a White House dominated organization established to provide the President and Kissinger with independent analysis and advice. Also of value in the Institutional (H-Files) are the National Security Study Memoranda/National Security Decision Memoranda (NSSM/NSDM) Files, containing requests for studies, the studies themselves, and resulting decision memoranda.
While the NSC Files and the NSC Institutional Files are the premier collections for Vietnam and Southeast Asia, additional useful collections exist in the Nixon Presidential Materials. For example, in the White House Special Files one finds the H. R. Haldeman Files, which holds Haldeman’s handwritten accounts of his daily activities. During his time at the White House, Haldeman at first wrote and later dictated a daily diary. Although not a foreign policy expert, he was a close confidant of the President and, as Chief of Staff, very close to, and observant of, the decision making process. His diary is a treasure trove of great historical significance. Available on compact disk (The Haldeman Diaries, the Multi-Media Edition), a selection of key entries have been published in book form by G. Putnam and Sons as The Haldeman Diaries: Inside the Nixon White House. Additionally, the Nixon Presidential Diary, an appointments diary indicating where the President was and with whom he met or spoke on a given day, is an essential tool for researchers and is found in the White House Central Files, Staff Member and Office Files.
The archival sources at the Ford Presidential Library in Ann Arbor, Michigan, offer the best coverage of the final months of the Vietnam war, including domestic political activities, the evacuation of Phnom Penh and Saigon, and the SS Mayaguez affair. The Presidential Country Files for East Asia and the Pacific contain invaluable documents, including memoranda, correspondence, telegrams, and reports. Organized by country name, there are 10 Hollinger boxes with materials exclusively related to U.S. involvement in Southeast Asia. The NSC East Asia and Pacific Affairs Staff Files offer additional documentation, including a chronological file, SS Mayaguez papers, and items generated for WSAG and NSC meetings. Valuable backchannel communications with Ambassador Martin and other Southeast Asian ambassadors fill 2 Hollinger boxes. Additionally, the library houses Ford administration H-Files, which include briefing books, memoranda, and WSAG meetings minutes produced during the U.S. evacuation of Cambodia and South Vietnam. A small collection of National Security Agency material at the Ford Library includes the text of helicopter radio communications during the April 1975 emergency. Researchers should also consult the Agency Files, NSC Vietnam Information Group Files, NSC Congressional Relations Files, NSC Meeting files, Kissinger and Scowcroft West Wing Files, Brent Scowcroft Daily Work Files, White House Central Files, Legislative Inter-Departmental Working Group Files, and Wolfgang Lehmann Papers. The library maintains detailed findings aids (available online) for each collection. There are also 10 Hollinger boxes of documents removed from the Embassy by Ambassador Martin during the evacuation, a unique collection considering the embassy staff destroyed or scattered most records covering the period from 1974 to 1975 during the final days in Saigon. Combined with the Martin backchannel messages, these records offer a detailed account of the Embassy’s experience, important considering the Ambassador’s great personal influence on the handling of the evacuation.
The Henry Kissinger Papers at the Library of Congress are likewise valuable. Although the collection is not open to the public, Kissinger permitted Department of State historians access to these records for use in the Foreign Relations series. Material in the papers often replicate documents found in other collections; it nonetheless holds some unique material. Foremost in this category are the transcripts of Kissinger telephone conversations based on notes taken by a secretary listening in on the phone at Kissinger’s office at the White House or transcribed from tapes recordings from his home telephone. Needless to say, the Kissinger telephone conversations are a key source for Vietnam War policy. While general researchers cannot use the transcripts at the Library of Congress, Kissinger has allowed copies to be transferred to the National Archives, where most are open to the public.
Other than the transcripts of telephone conversations, Kissinger’s speeches and writings, and his Record of Schedule (appointment diary), the Kissinger Papers are segregated into a classified file (secret and below), a top-secret file, and a section containing a limited amount of restricted data and special compartmentalized information. In this material, the best collection for Vietnam and Southeast Asia is the Geopolitical File, which contains a wide-ranging section on Vietnam and smaller files on Cambodia and Laos. Also of value within the Kissinger Papers are the Memoranda to the President File, the Memoranda of Conversations File, and the Presidential File. However, none of these deal exclusively with Vietnam and Southeast Asia.
The Department of State, Department of Defense, and to a lesser extent the Central Intelligence Agency, although strong bureaucratic players in the Johnson Administration’s policymaking, played a reduced role under President Nixon and Henry Kissinger, who concentrated policymaking in the White House. The files of the Department of State, especially the Central Files and certain Lot Files, are valuable for tracking events in Vietnam, Laos, and Cambodia, and at the Paris Talks. Before Kissinger became Secretary of State in September 1973, Department of State records offer poor coverage of U.S. policy toward Southeast Asia, because Nixon and Kissinger intentionally excluded the Secretary of State and the Department from the Vietnam decision-making process. Still, some of the Central Files are useful for political, economic, and military developments in Southeast Asia from 1969 to 1974, including POL 27 CAMB/KHMER, POL 27 LAOS, and POL 27 VIET S. While ostensibly the designation for military operations in Vietnam, and to a lesser extent Laos and Cambodia, POL 27 became a catchall file. Consequently, it is a good source of material for those interested in political developments in Saigon, Vientiane, or Phnom Penh. In the Lot Files one finds Ambassador Ellsworth Bunker’s weekly and later monthly summaries of events in South Vietnam to President Nixon. They covered in detail the government, politics, the economy, and the war. Although the President rarely read the reports, they nonetheless provide a useful account of important events in South Vietnam; they have been collected and published as The Bunker Papers, Reports to the President from Vietnam, 1967–1973 (Berkeley, 1990). The Central Files offer Vietnam-related documents through mid-1973, after which the Department captured memoranda, telegrams, and other records electronically. Researchers can search and retrieve these later items through a National Archives archival database.
Beginning in September 1973, when Kissinger became the Secretary of State, the Department again played an active role in the policymaking process. The Records of Henry Kissinger (26 Hollinger boxes), 1973–1977, Entry 5403, Record Group 59, at the National Archives contain documents related to Vietnam. The Transcripts of Secretary of State Kissinger’s Staff Meetings (11 Hollinger boxes), Entry 5117, Record Group 59, are also useful. Researchers may likewise consult the U.S. Foreign Service post records. Although they offer little on high policy, the post files are filled with reports and communications on local conditions and activities. In the absence of U.S. initiative after mid-1973, moreover, the story of U.S. involvement in South East Asia often centers on embassy activity. The post files, however, provide inconsistent coverage of U.S. activities abroad because many records did not survive the fall of Saigon. The best preserved, the Phnom Penh Embassy Files, Record Group 84, offer detailed coverage of U.S. activities in Cambodia. Large portions of the Saigon Embassy collection, on the other hand, were lost in 1975. The most complete collection of Saigon Embassy documents for the period from 1974 to 1975 is located at the Ford Library, not the National Archives. Also, while they offer thin coverage of the years between 1969 and 1974, the Lot Files of the Bureau of East Asian Affairs Files, Record Group 59, can be useful for researchers interested in the ending of the Vietnam War.
The Central Intelligence Agency (CIA) records are essential for documenting the role of intelligence in the war in Southeast Asia. Even so, the most important finished intelligence can be found in the Nixon Presidential Materials, NSC Files. The CIA prepared a daily briefing for the President on Vietnam that is in the National Security Council Files, President’s Daily Briefings. Additionally, useful collections under CIA’s physical custody are the National Intelligence Center (NIC) Files, which contain many intelligence estimates and memoranda. Of particular significance are the records of George Carver, Special Assistant for the Director of Central Intelligence (DCI), for Vietnam Affairs. As the CIA’s foremost Washington expert on Vietnam and Southeast Asia, his files are central to understanding the interplay between intelligence and foreign policy. The same is true for the DCI (Helms) Files and DCI Executive Registry Files, although these files also include material on non-Vietnam issues that engaged the DCI. The National Intelligence Council’s Estimative Products on Vietnam, 1948–1975, published in 2005, contains a good selection of intelligence estimates on Vietnam. In most cases, Foreign Relations volumes print only the summaries of the National Intelligence and Special Intelligence estimates while the full texts are published in the in the NIC publication. Intelligence Files for the Nixon and Ford Administrations, including the records of the 303 Committee/40 Committee and related subject files for Vietnam and Southeast Asia were particularly valuable for documenting covert operations and unconventional warfare. They are currently in the custody of the National Security Council, but are destined for the Nixon and Ford Presidential Libraries. A Department of State Lot file, the INR/IL Historical Files, holds valuable material for these topics and is similar to the Nixon Intelligence Files. These files remain in the control of the Department of State.
The Department of Defense and Secretary of Defense Melvin Laird were key players in the formation of policy towards Vietnam. Department of State historians conducted extensive research in the Department of Defense records now housed at the Washington National Records Center in Suitland, Maryland. Still classified, these files include secret and top-secret documents, organized by office, year, and subject. These files will likely move to the National Archives in College Park upon declassification. The Defense Secretary’s key memoranda are almost always in the NSC Files in the Nixon and Ford collections.
At the Ford Library, a collection of documents covers Laird’s tenure as Secretary of Defense. His staff chose these Laird Papers at the end of his term as Secretary of Defense with a view to documenting his major decisions and accomplishments. The Papers of James R. Schlesinger, Secretary of Defense from 1973 to 1975, are located at the Library of Congress. Schlessinger’s collection holds memoranda, reports, and communications related to his government service, but is not yet open to the public. Major portions of the Laird and Schlesinger collections concern Vietnam, Cambodia, and POW/MIA affairs. In addition, the official files of the Secretary of Defense, Under Secretary of Defense, and their Assistants, plus the records of the Assistant Secretary of Defense for International Security Affairs, have large sections devoted to Vietnam and Southeast Asia.
Defense related records that were not available when the first volumes were being researched, but are worthy of mention as sources, are the records of the Chairman of the Joint Chiefs in Record Group 218 at the National Archives—specifically those of General Earle G. Wheeler, Chairman, 1964–1970; Admiral Thomas H. Moorer, 1970–1974; and General George S. Brown, 1974–1978—in the National Archives. The most useful sections of these records are the Chairman’s correspondence to and from the Commander, Military Assistance Command, Vietnam, correspondence to and from the Commander in Chief, Pacific Command, and additional miscellaneous Vietnam related documents in various country folders.
Another JCS collection, Admiral Moorer’s Diary, reveals significant information about the policymaking process. Only made available when the final Foreign Relations volumes in the Vietnam series were being researched, the Diary contains entries for practically every day during his tour of duty as Chairman. Each day’s entry contains a series of sub-entries about meetings (in his office, in Secretary Laird’s, at the White House, or elsewhere), telephone conversations, or reflections on policy matters and other topics. Appended to most daily entries are one or more documents. Especially useful to the researcher are memoranda for the record Moorer drafted after meetings with President Nixon or with Kissinger, internal memoranda from one of his own subordinates or external ones from Kissinger or Kissinger’s Deputy, Alexander M. Haig, or from other members of the Nixon Administration. What gives special value to the already immensely valuable diary and its attached documents is that Moorer taped and transcribed many of his telephone conversations and attached the transcripts to the Diary. These transcripts of conversation—a few with Nixon but more often with Kissinger; Haig; Laird; Admiral John S. McCain (Commander in Chief, Pacific); Generals Creighton W. Abrams and Fred C. Weyand (theater commanders in Saigon); and the Admiral’s own senior subordinate at the Pentagon—reveal the extraordinary and substantial role Moorer played in the formation and implementation of U.S. national security policy in Southeast Asia.
After February 1971, the White House Presidential Recordings are a critical source for understanding Vietnam policy developments and to a lesser extent for policy in Cambodia and Laos. The recordings that are transcribed and cited in the Foreign Relations volumes comprise only a small portion of the recordings available. Using the tape log, and comparing entries with the meetings and conversations for which there are written records, the editors and the Nixon Tape team at the Office of the Historian have selected policy-significant recordings of meetings and telephone conversations. While tape conversations are difficult to transcribe and do not always lend themselves easily to insertion in documentary publication, the selection presented in these volumes is a representative of the larger body of conversations. Nixon and his close confidants spent hours talking in the President’s Oval and Executive Office Building office. Their conversations were often unstructured and repetitive, their language frank, raw, and often uncomplimentary to individuals and institutions. While it is the immediacy and apparent unguarded natured of recorded conversations, whether of individuals talking on a telephone or in an office, that give such conversations the reputation for truthfulness they enjoy among historians and others, it should be emphasized that it is just as possible to shade the truth, or lie, in conversations as it is in the more calculated act of writing. At the same time, when recordings exist, as the Nixon White House tapes do, they become an integral part of the historical record and impose on historians the obligation to exploit them as best they can. These tapes are an almost breathtaking resource but must be used with caution and viewed within the broader context. Volumes in the Foreign Relations series provide just such a context.
What makes the Nixon administration’s records on Vietnam especially revealing is the existence of these unique sources. The presidential tapes recordings, the Kissinger telephone conversations, the Haldeman Diaries, and the Moorer Diary and telephone conversations provide an added dimension of documentary material. Taken in conjunction with the more traditional records, these special sources deepen one’s understanding of the characters involved and how they interacted with others and with the circumstances they encountered. By extension, they also provide a great understanding of the policymaking process.
In sum, the records of the Nixon and Ford administrations on Vietnam are a rich and abundant resource but pose some substantial challenges to researchers. Even with five volumes covering the conflict from 1969 to 1975, only a small fraction of the total documentation will be printed in the Foreign Relations series. The editors of these volumes believe, however, that they have selected the most significant documents available for understanding the policy process. Furthermore, they have added value to their selections through annotation and editorial notes. While Department of State historians have had to make difficult choices, they believe that the resulting documentary collections provide a solid account of policy decisions by the Nixon and Ford Administrations on the Vietnam War and will stimulate additional research on U.S. involvement in the still-controversial war.