President Richard Nixon believed that years of aerial bombing in Southeast Asia to pressure North Vietnam achieved “zilch” even as he publicly declared it was effective and ordered more bombing while running for reelection in 1972, according to a handwritten note from Nixon disclosed in a new book by Bob Woodward.

Nixon’s note to Henry Kissinger, then his national security adviser, on Jan. 3, 1972, was written sideways across a top-secret memo updating the president on war developments. Nixon wrote: “K. We have had 10 years of total control of the air in Laos and V.Nam. The result = Zilch. There is something wrong with the strategy or the Air Force.”

The day before he wrote the “zilch” note, Nixon was asked about the military effectiveness of the bombing by Dan Rather of CBS News in an hour-long, prime-time television interview. “The results have been very, very effective,” Nixon declared.

Nixon’s private assessment was correct, Woodward writes: The bombing was not working, but Nixon defended and intensified it in order to advance his reelection prospects. The claim that the bombing was militarily effective “was a lie, and here Nixon made clear that he knew it,” Woodward writes.

Nixon’s note, which has not previously been disclosed, was found in a trove of thousands of documents taken from the White House by Alexander P. Butterfield, deputy to H.R. Haldeman, Nixon’s chief of staff, and not made public until now. Butterfield’s odyssey through Nixon’s first term is the subject of Woodward’s book, “The Last of the President’s Men,” to be published Tuesday by Simon & Schuster.

Butterfield became a key figure in the Watergate scandal when he revealed to Senate investigators the existence of the White House taping system. The tapes captured Nixon’s role in the coverup and marked a critical turning point in the collapse of his presidency. He resigned in 1974. Woodward and Carl Bernstein exposed the Watergate story in The Washington Post.

The new book, based on the documents and more than 46 hours of interviews with Butterfield, offers an intimate but disturbing portrayal of Nixon in the Oval Office. Butterfield depicts Nixon, who died in 1994, as forceful and energetic, but also vengeful, petty, lonely, shy and paranoid.

Butterfield felt deeply conflicted; he was proud to be serving but chagrined to be caught up in the underside of Nixon’s presidency. “The whole thing was a cesspool,” he told Woodward.

Butterfield, now 89, was in charge of preventing other Nixon staffers from leaving the White House with government documents, but he saw many, including the late Nixon counselor Arthur Burns, haul away boxes when they left.

Butterfield anticipated writing a memoir, so when he left the White House in 1973, “I just took my boxes of stuff and left,” he told Woodward, packing them into his and his wife’s car. Woodward writes that the boxes contained everything from routine chronologies and memos to some top-secret exchanges with Kissinger and a few highly classified CIA bulletins.

Butterfield acknowledged to Woodward that it was improper and wrong to remove them, and pledged to ensure that they will be deposited with a proper archive.

Woodward, who wrote that he thought the Nixon story was over for him after his book on Mark Felt, the FBI associate director and secret source known as Deep Throat, said he was “shocked” at the existence of Butterfield’s secret files. “So the story, like most of history, does not end,” he writes.

The Vietnam War had been all-consuming for Nixon’s presidency. The antiwar movement was strong in the United States, and Nixon was under political pressure to end the conflict. The centerpiece of Nixon’s approach was “Vietnamization”: withdraw U.S. troops so the South Vietnamese could take over, and negotiate a peace settlement “with honor,” avoiding anything that could be labeled a defeat.

As ground troops withdrew, air power was one of Nixon’s few remaining tools to pressure Hanoi. In late December 1971, Nixon ordered renewed bombing of North Vietnamese targets for five days.

By early 1972, Nixon was on the verge of announcing his reelection campaign and taking his momentous trip to China. But he was worried about reports of a major North Vietnamese buildup, foreshadowing a possible offensive.

On Jan. 2, 1972, in the CBS television interview, Rather asked Nixon, “On everyone’s mind is the resumption of the widespread bombing of North Vietnam. Can you assess the military benefits of that?” Nixon reiterated what he had often said about the bombing, that it was “very, very effective,” and added, “I think that effectiveness will be demonstrated by the statement I am now going to make.” Nixon then announced that he would soon bring home more troops — virtually removing any U.S. combat force in Vietnam.

Woodward said he could find no evidence that the study was ever carried out.

In another memo written a few months later, also found in the Butterfield files, Nixon complained to Kissinger that the military and bureaucracy were too timid. Nixon demanded action that is “strong, threatening and effective” to “punish the enemy” and “go for broke.” Nixon may also have been frustrated at North Vietnamese resilience. Woodward cites CIA, Defense Intelligence Agency and Pentagon memos showing that the bombing was not that effective because the North was getting more supplies than it needed to fight the ground war in the south, and could hold out for two years even if the bombing continued.

Kissinger, in an interview, told Woodward he agreed with the conclusion that years of bombing North Vietnam had failed, and he recalled that Nixon was frustrated. “He was in the habit of wanting more bombing . . . his instructions most often were for more bombing,” Kissinger said.

Woodward writes: “The ‘zilch’ conclusion had grown over three years. In what way and when did he realize this? History may never know. Maybe Nixon never knew, never grasped the full weight of his own conclusion.”

Woodward concludes that while Nixon knew the bombing was militarily futile, he believed it would reap political rewards at home. After Nixon resigned, papers found in his hideaway office in the White House included a GOP polling study, commissioned in 1969, that showed that the American people would favor bombing and blockading North Vietnam for six months. Woodward cites the work of Ken Hughes of the University of Virginia’s Miller Center to show that “the massive bombing did not do the job militarily but it was politically popular. Hughes argues with a great deal of evidence that the bombing was chiefly designed so Nixon would win re-election.”

The “zilch” note was followed in February by orders for intensified bombing of North Vietnam. On May 8, Nixon ordered the mining of Haiphong Harbor and bombing of key military targets. On Sept. 8, Nixon reported to Kissinger that poll numbers favored the bombing. “It’s two-to-one for bombing,” he boasted.

On Oct. 16, just weeks before the election, Nixon recalled the May 8 decision to mine the harbor and told Kissinger, “May 8 was the acid test. And how it’s prepared us for all these things. The election, for example.” Kissinger replied, “I think you won the election on May 8.” Nixon was reelected by a landslide in November.

In that election year, the United States dropped 1.1 million tons of bombs in the Vietnam War, including 207,000 tons in North Vietnam alone, Woodward reports, citing Pentagon records.

Before joining the White House, Butterfield was a 42-year-old U.S. Air Force colonel with an assignment in Australia. After Nixon’s triumph in the 1968 election, Butterfield reached out to Haldeman, an acquaintance from their university years at UCLA. Haldeman then hired Butterfield as his White House deputy. Butterfield was an outsider, unlike many of the others around Nixon, and what he saw in the next four years left a vivid impression.

When Butterfield was introduced to the president in the Oval Office by Haldeman, Nixon mumbled, cleared his throat and gestured. “No words came out, only a kind of growl,” Woodward writes, based on Butterfield’s recollection. Another time, also in the White House, Nixon dropped by a birthday party for Paul Keyes, a comedy writer and Nixon friend who had helped on the 1968 campaign. When Nixon entered the room, there was an unnatural hush. No one offered a handshake or a glass of wine. Nixon seemed at a loss. Keyes was wearing a solid green blazer. “Ah, ah, ah . . . uh,” Nixon muttered, according to Woodward’s account. “Then Nixon pointed down at the carpet, a worn, faded maroon. He spoke in a deep but barely audible voice. ‘Green coat . . . red rug . . . Christmas colors.’ He then wheeled around and strode out of the room to the Oval Office.”

Woodward says Butterfield felt that “Nixon was quickly becoming the oddest man he’d ever known.”

“It was if he were locked in his own deeply personal world, thinking, planning and churning,” Woodward writes of Butterfield’s impressions. Butterfield described Nixon as so lonely that he often took dinner by himself in the Old Executive Office Building, sitting with his suit coat still on, writing on his legal pad. “He was happiest when he was alone,” Butterfield recalled.

Nixon’s relationship with his wife, Pat, was cold, Butterfield observed. At the Winter White House, a compound in Key Biscayne, Fla., she stayed in a separate house.

On Christmas Eve 1969, Nixon walked through the Executive Office Building adjacent to the White House to wish employees a merry Christmas. The president discovered that some support staff employees had prominently displayed photographs of President John F. Kennedy — and that one worker had two. Nixon was furious and ordered Butterfield to remove all photos of other presidents. On Jan. 16, 1970, Butterfield wrote a memo to the president, titled “Sanitization of the EOB,” describing how all 35 offices displayed only Nixon’s photograph.

Butterfield learned that Nixon did not just have an “enemies list” with dozens of names, but also an “opponents list” and a “freeze list.” One day Nixon exploded in anger after finding out that Derek Bok, then the president of Harvard University, was at the White House. “I don’t ever want that son of a bitch back here on the White House grounds,” he told Butterfield. “And you get those enemies lists, make sure everybody knows who’s on them.”

[Kissinger: the Dr. Frankenstein of foreign affairs, or just self-promoter?]

The president constantly scrutinized event invitation lists, striking names. Nixon organized a procedure with Butterfield so that during coffee after a state dinner, only a pre-selected group of five out of some 100 invited guests would get a chance to talk to the president. No one else could approach him.

Butterfield told Woodward that Nixon was controlled by “his various neuroses, the deep, deep, deep resentments and hatreds — he seemed to hate everybody. The resentments festered. And he never mellowed out.”

Butterfield did not know about the specifics of the Watergate break-in, but witnessed how Nixon’s obsessions led to it. At one point, Butterfield was given the assignment to plant a spy in the Secret Service detail of Sen. Edward M. Kennedy (D-Mass.). Nixon later mused that the spy — a retired agent who was reactivated — might find information that would “ruin him for ’76,” when Kennedy might be considered a possible presidential candidate. Butterfield knew the plan was illegal, and told Woodward that he was surprised at himself for going along with it.

It fell to Butterfield to organize the White House taping system, installed at Nixon’s behest in February 1971. Although Nixon endlessly explored and sifted his options on most issues, Woodward reports that “there was apparently no discussion about the merits or risks of such a taping system.” It was installed over a weekend by the Secret Service while the president was out of town. Five microphones were put in the president’s desk, on the top, concealed with a coating of varnish. The lights on the mantel in the Oval Office also carried microphones, a place where Nixon often took guests, including heads of state, to chat. The microphones were connected to voice-activated tape recorders behind a metal door in the basement.

When the Watergate scandal broke, “I was thinking of the tapes the whole time,” Butterfield recalled. “God, if they only knew. If they only knew. In a way I wanted it to be known. In the deep recesses of my brain, I was eager to tell.” Woodward devotes several chapters to Butterfield’s personal struggle over whether to reveal the secret taping system, which Nixon thought would never be made public.

On the day of Nixon’s departure from the White House, Aug. 9, 1974, Butterfield saw many White House officials and workers weeping in the East Room. “I could not believe that people were crying in that room,” he told Woodward. “It was sad, yes. But justice had prevailed. Inside I was cheering. That’s what I was doing. I was cheering.”