Secrets is Daniel Ellsberg's account of a cold warrior's slow metamorphosis to dissident, then releasing the Pentagon Papers to the media in an attempt to end the war in Vietnam under Nixon. He spent years in Vietnam learning first hand how corrupt the South Vietnamese elites were and how badly the war was going, even with massive US support and troops. As a Rand, Defense Department, State Department insider he learned how bad the decision making had been through five presidents beginning with Truman to get to this position, plus the distortions and lying to the press and public.
The Japanese pulled out of Vietnam in 1945, effctively granting independence to the country under Ho Chi Minh. The French returned, essentially granting Ho independence in the north and promising free elections. The French renigged and then attacked the north to claim the whole country. Mao took control of China in 1949 and the American question was "who lost China?" The Chinese supported Ho and the French lost interest in the attack. But Truman provided most of the cost of the French effort which continued until Dien Bien Phu in 1954. The Geneva Conference temporarily divided the country with the idea of forthcoming elections. The US under Eisenhower continued support including advisors, facing a growing insurgency by the Viet Cong (supported by the north and China). The South Vietnamese elite (including the military) was corrupt, mainly Catholic landowners, while most of the people were Buddhist peasants. Free elections were out of the question.
The US engineered minor attacks around the Gulf of Tonkin provoking the north to respond which they eventually did (the US lying about their role). This resulted in the Gulf of Tonkin Resolution, turning into a declaration of war. Johnson expanded the war to over half a million Americans essentially to avoid a total collapse of the South's military, then incompetent strategies that proved ineffective excepts for the killing of thousands of Americans and vastly more Vietnamese. Lies at all levels (except for secret analysis showing the opposite, some of it written by Ellsberg) claiming the south was winning and the war would soon be over. [This was certainly the story I got when I was in the Army beginning in 1968.] In 1968 Johnson did not run for reelection and Nixon, a Republican was elected.
Nixon claimed an entirely new approach, leading most Americans to believe that his strategy involved the slow pullout of US troops and turning the war over the the South Vietnamese. Ellsberg determined that Nixon in fact would expand the war to Cambodia and Laos and substantial bombing of the north. [Nixon did, causing even more destruction and loss of life than under Johnson.] It was at this point thar Ellsberg decided to release the Pentagon Papers, a history of the war (that is, the real history) through 1968. Roughly the last half of the book was about this process, including the illicit (much of it illegal) response of the Nixon administration. CREEP plumbers Colson and Hunt seemed to do much of the illegal stuff (breaking into Ellsberg's psychiatrist's office, breaking into Democratic headquarters in the Watergate, forging documents about Ellsberg, even Kennedy's presidency, and so on). The Nixon response was cover up, that is, obstruction of justice. Thus, Ellsberg was in the middle of the Watergate conspiracy, which brought down Nixon. The Ellsberg case was thrown out and the Vietnam War ended, with a total US/South Vietnam defeat--the answer that was obvious at least by 1954.
This question I have is how this could happen over 30 years of bad decisions, deceit, and worse. Most of the people involved on our side were intelligent, well educated and experienced, and (at least in the beginning) honorable. This basic pattern repeated itself in Afghanistan and Iraq (at Mark Twain said: "History doesn't repeat itself, but it rhymes"). Somewhere in psychology there should be a Cassandra Syndrome, with the early prophets predicting exactly what will happen, to be ignored by everyone. Note that in Homer's tale Cassandra was cursed.