The U.S. National Archives has released the complete “Pentagon Papers,” 40 years after parts of the secret government study first appeared in The New York Times.

The then-classified study by the U.S. Defense Department showed the United States was secretly escalating the conflict in Vietnam while misleading Congress, the American public and U.S. allies. The disclosure solidified opposition to the war and increased mistrust of government.

The study, commissioned in 1967 by then Secretary of Defense Robert McNamara, covered U.S.-Vietnam relations dating back to 1945.

A forerunner of the WikiLeaks document disclosures, publication of the Pentagon Papers started a national discussion on freedom of the press and government transparency.

Former military analyst Daniel Ellsberg began leaking parts of the classified study to The Times early in 1971. President Richard Nixon tried to halt the publication of the secret documents, and the battle went all the way to the Supreme Court.

While most of the study has been out for years, Monday's release draws the information together for the first time, and makes it available online. The documents were also released by the John F. Kennedy, Lyndon Johnson and Richard Nixon presidential libraries.