A newly declassifed memo to Nixon from his secretary of defense at the time reflects just how much the administration felt and discussed public pressure - even as it weighed U.S. geopolitical strategy - in anguished internal debate over war policy.
The seven-page document cautions the president against a proposal from the military brass to conduct a high-intensity air and naval campaign against North Vietnam.
Then-Defense Secretary Melvin Laird said such a plan would involve the United States in "expanded costs and risks with no clear resultant military or political benefits."
With peace talks "seemingly stalled in Paris, with combat activity levels reduced in South Vietnam, but with seemingly rising levels of discontent in the United States, we should review the overall situation and determine the best course of action," the defense secretary writes the president on Oct. 8, 1969.
"The sum total of the considerations ... casts grave doubt on the validity and efficacy" of the proposal from the Joint Chiefs of Staff at the Pentagon, the memo concludes.
At the time of Laird's memo, the Nixon administration was secretly conducting a massive bombing of Cambodia to destroy sanctuaries for North Vietnamese enemy troops.
The Nixon administration didn't go forward with the Joint Chiefs' plan at the time, but did so in December 1972, launching what became known as the "Christmas bombing" of Hanoi when peace talks hit a dead-end. The effort stirred anger with the American public. North Vietnam called it a terrorist act.
Laird became the biggest proponent of the concept called Vietnamization, urging Nixon to follow through on a policy of troop withdrawals, putting the burden of fighting the conflict on South Vietnamese troops.
The massive B-52 strikes over Hanoi and Haiphong in the last two weeks of December 1972 were a gambit to shock North Vietnam into a serious posture in peace negotiations. The newly released tapes cover the period leading up to the bombing as well as the execution and are expected to include Oval Office discussions about the assault.
The recordings are of Nixon's White House conversations from November 1972 to January 1973 and cover his re-election that fall, steps to bomb North Vietnam and also to make peace with it.
Historians hoped for insights into the 1972 "Christmas bombing," one of the most controversial acts in a divisive war and the most concentrated air attack of the conflict.
The documents take historians closer than the latest tapes do to the Watergate scandal that gathered force in 1973 and peaked with Nixon's resignation in disgrace in August 1974.
The records include 65,000 pages from the files of J. Fred Buzhardt, Nixon's attorney in the titanic struggle over White House tapes that ultimately betrayed Nixon's complicity in the scandal.
Other Watergate figures are represented in the collection, too. Thousands of pages are being released from the files of Nixon aides Charles W. Colson, H.R. Haldeman, Patrick J. Buchanan and John W. Dean.
As well, there are more than 8,000 pages of correspondence from and to Nixon's political lieutenants at the Committee to Re-Elect the President, John Mitchell and committee deputy Jeb Magruder.
Burglars working for the committee broke into Democratic headquarters at the Watergate complex in June 1972, setting off a chain of events that tied Nixon's top men and the president himself to a cover-up of illegal political machinations.
Over the years, a mountain of paper and tape has emerged shedding light on the inner workings of a president who operated in great secrecy but, ironically, seemed to chronicle every step for history.
This is the 12th release of Nixon White House tapes since 1980. More than 2,200 hours of tape recordings from the Nixon White House now are available, according to the National Archives, which joined the Nixon presidential library in Yorba Linda, Calif., in releasing the material Tuesday.
All the recordings in the latest release are being put online while the papers can be seen at the two institutions.