The Pentagon Papers were a top-secret US Defense Department study that gave a historical analysis of the United States’ political and military involvement in Vietnam from 1945 till 1967.
The official name of this study was “Report of the Office of the Secretary of Defense Vietnam Task Force.” However, in the public space and in media, this study was commonly known as “Pentagon Papers.”
Robert S McNamara, who had served as the Defense Secretary in both the Kennedy and Johnson administrations, commissioned this study in June 1967.
To this day, it is not very clear what might have been the exact motivation behind McNamara’s actions; we could only speculate.
As per McNamara himself, his aim was to leave behind a proper history of the US involvement in Vietnam for future historians and policymakers to refer to. The study could serve as a reference point and help prevent future policy errors.
It has also emerged that President Johnson and the top military brass were not happy with having McNamara as the Defense Secretary. For them, he had become an impediment in realizing their Vietnam War objectives.
McNamara too was disenchanted with the approach being adopted by the Johnson administration. He was convinced of the futility of the war and knew well enough that it was unwinnable. He was quite disturbed by the broadening scope of the war and the increasing number of casualties.
McNamara created a secret unit within the Pentagon, the Vietnam Study Task Force, to work on this study. He kept the commissioning of this study a secret from the then US President Lyndon B. Johnson, the Secretary of State Dean Rusk, and the National Security Advisor Walt W. Rostow.
McNamara, later on, did admit that it was a mistake on his part to have kept Johnson in the dark about commissioning of this study.
The study was commissioned in June 1967 and was completed by February 1969, that is, around 1.5 years.
McNamara himself did not receive the completed study. He left office in February 1968 itself. It was his successor, Clark Clifford, who received the completed study in February 1969. After McNamara’s departure, the work on the study continued under Leslie H. Gelb as the project director.
The entire study is bound into 47 volumes consisting of a total of around 7000 pages, which includes 4000 pages of classified government documents and 3000 pages of historical analysis of those documents.
Around 36 military analysts worked on this study. To keep the study a secret, the analysts did not conduct any interviews with any member of the armed forces, the White House staff, or any other government agency or department personal, retired or serving. They relied on the documents available in the Department of Defense and other cross-departmental documents from various other government agencies and departments such as the State Department and the Central Intelligence Agency (CIA).
Daniel Ellsberg, a military analyst who had worked on the study himself, leaked the Pentagon Papers to The New York Times, the Washington Post, and other publications in 1971.
The most important of the Pentagon Papers’ revelations was that successive US administrations, starting from Truman administration up till Johnson administration, had systematically lied to the American public and also to the United States Congress about the United States’ involvement in Vietnam.
You can read the Pentagon Papers online, in its entirety, in a PDF format on the National Archives website.