Secretary of Defence, Robert McNamara, was the man tasked with overseeing America's war in Vietnam. In 1967, he ordered a secret report on the history of American military involvement with Vietnam since 1945. It came to 7,000 pages in 47 volumes. The report revealed that the real cause of the war was not to preserve south Vietnam's independence from the north, but to contain China.
It also exposed the United States' role in helping President Diem into power, and allowing the coup against him that pledged a full scale war.
Additionally, it revealed how America had secretly expanded its bombing campaigns in Cambodia.
When analyst, Daniel Ellsberg, leaked the report in 1971, he was charged with espionage and theft of government property by the Nixon Administration. Nixon's agents also spied on Ellsberg's home and burgled confidential files from his psychiatrist.
The president put in junctions on the New York Times and Washington Post for attempting to publish the reports. The alleged full pentagon papers weren't published until 2011.