Woodward and Bernstein adapted this piece from their 1976 book, "The Final Days." This excerpt is appearing both in The Washington Post and on CNN.

(CNN) We're here again. A powerful and determined President is squaring off against an independent investigator operating inside the Justice Department. Special counsel Robert Mueller's mission is a comprehensive look at Russian meddling in the 2016 election -- and any other crimes he uncovers in the process. President Donald Trump insists it's all a "witch hunt" and an unfair examination of his family's personal finances. He constantly complains about the investigation in private and reportedly asked his White House counsel to have Mueller fired. No wonder many people are making comparisons to the Saturday Night Massacre of 1973, when President Richard Nixon fired special prosecutor Archibald Cox, and Attorney General Elliot Richardson and Deputy Attorney General William Ruckelshaus resigned.

We covered that eerily similar confrontation for The Washington Post 45 years ago. Nixon didn't know it at the time, but the Saturday Night Massacre would become a pivot point in his presidency -- crucial to the charge that he'd obstructed justice. For him, the consequences were terminal. A retelling of the episode, adapted from "The Final Days," as we called our book on the president's last year, can illuminate the stakes.

• • •

In April 1973, Nixon persuaded Richardson, his defense secretary, to switch departments and become the attorney general. The president invited him to a Camp David meeting that turned out to be part of the Watergate cover-up: He wanted to ensure that Richardson would be an ally in a new Watergate investigation.

Richardson's chilly, formal manner evoked the Eastern, academic establishment that Nixon despised. The slow, winding rhetoric that weighed down his conversation drove the president to distraction. Still, he needed Richardson, with his impeccable reputation, to redeem his Justice Department and take charge of the Watergate investigation.

Nixon told him that the investigation must be thorough and complete, though there might be some areas of national security that would have to be left alone. "You must pursue this investigation even if it leads to the president," Nixon said, and his eyes met Richardson's. "I'm innocent. You've got to believe I'm innocent. If you don't, don't take the job."

Vastly relieved, Richardson nodded his acceptance: Nixon, he thought, would never set such an investigation in motion unless he was innocent.

"The important thing is the presidency," Nixon continued. "If need be, save the presidency from the president."

Richardson, writing on a legal pad, paraphrased the thought: "If the monster is me, save the country."

Almost immediately he appointed his old Harvard law professor, Archibald Cox -- who had served as President John F. Kennedy's solicitor general -- as special prosecutor to handle Watergate, promising him full independence. Cox set about investigating, and three months later he subpoenaed nine of the White House tapes.

Nixon did not take kindly to this. White House chief of staff Alexander Haig warned Richardson that the president might fire Cox if he weren't reined in, shaking Richardson's faith in the president's innocence. "If we have to have a confrontation, we will have it," Haig told him.

A few days later, Haig said he had advised the president to turn over the tapes, but Nixon had refused. The president would resign first. Haig told Richardson he didn't know whether the president was hiding something or whether he was merely concerned about the principle of confidentiality, but he had never seen Nixon so worked up. "It makes you wonder what must be on those tapes," said Haig, who himself was only a few months into the job.

For now, Richardson decided to give Nixon the benefit of the doubt while he oversaw his department's investigation of Vice President Spiro Agnew, who had been accepting illegal cash payoffs from contractors for years, starting when he was a Maryland official.

In October, Richardson was leaving an Oval Office briefing about the Agnew situation when Nixon called after him. "Now that we have disposed of that matter, we can go ahead and get rid of Cox." Richardson didn't know how to take the remark. But soon the issue would come to a head.

• • •

President Richard Nixon in January 1973.

On Monday, October 15, the United States Court of Appeals for the District of Columbia ruled that the president, who had fought the order to turn over the nine subpoenaed tapes, must hand them over -- unless the White House could reach "some agreement with the Special Prosecutor" out of court. Nixon had until midnight Friday to comply, to appeal to the Supreme Court or to reach a compromise with Cox. Richardson was doubtful that the White House and Cox could agree on much of anything in five days.

After the court decision came down, Haig and White House lawyer J. Fred Buzhardt summoned Richardson. They presented the attorney general with a plan: Nixon would personally listen to the subpoenaed recordings and supervise the preparation of transcripts that would be turned over to the court as a substitute for the tapes. Cox -- long a bone in Nixon's throat and a bad idea in the first place -- would be fired. And there would be no more litigating over other tapes.

Richardson, outwardly calm, raised an objection. The plan was contrary to the agreement he had made with the Senate Judiciary Committee during his confirmation hearings. He had promised that the special prosecutor could be removed only for "extraordinary improprieties." If he were ordered to fire Cox, he might instead have to resign himself.

Haig and Buzhardt held their ground. Cox would have to go. Richardson left the White House bewildered and uncertain of what would happen next.

Haig called him 40 minutes later to suggest a compromise: Sen. John C. Stennis, the 72-year-old Mississippi Democrat who chaired the Senate Armed Services Committee, would be asked to make a comparison between the transcripts and the tapes. His authenticated version would be submitted to the court. (No mention was made of the fact that the senator was partially deaf and that the tapes were difficult to hear under the best of circumstances.) If Richardson accepted, Cox would not have to be fired, but Richardson would forbid any further demands for tapes. The president, Haig added, would expect Richardson's support if it came to a showdown with Cox.

Later that day, Richardson called Haig back and made it clear that he was committed only to the Stennis authentication of the nine subpoenaed tapes. He couldn't make any other promises.

Now Richardson had to sell the Stennis compromise to Cox, who wanted to see the terms in writing. Richardson drafted an agreement that said it would "cover only the tapes heretofore subpoenaed by the Watergate grand jury at the request of the Special Prosecutor." When he sent it to the White House on Wednesday morning, October 17, Buzhardt cut that section. The president, he knew, didn't ever want to hear about future requests for tapes. The White House also wanted to empower Stennis to "paraphrase language whose use in its original form would in his judgment be embarrassing to the President."

Richardson wanted to avoid a confrontation with Nixon, and he acquiesced. But Cox flatly rejected the compromise. "The public cannot fairly be asked to confide so difficult and responsible a task to any one man operating in secrecy, consulting only with the White House," he wrote to the attorney general on Thursday afternoon. And Cox wanted an agreement that would "serve the function of a court decision in establishing the Special Prosecutor's entitlement to other evidence." A court might want the actual tapes, the best evidence, for any trial.

Richardson took Cox's memo to a 6 p.m. meeting at the White House. Haig was unaccepting. The White House was seeking a compromise, he said, and Cox was making it impossible. He should be fired, Haig said. Three other Nixon lawyers in the meeting agreed. They were confident that the president could convince the public he'd acted reasonably.

Richardson did not think so. He made it clear that he could live with Cox's voluntary resignation but that he could not fire him for refusing the Stennis plan.

Later that night, Richardson sat in his study in McLean, Virginia. The rush of the Potomac River was barely audible in the distance. He wrote at the top of a yellow legal pad: "Why I Must Resign." He was sure that Cox could not be persuaded to acquiesce, and he knew that the president wanted Cox out.

Richardson's first reason for resigning was his promise to the Senate to guarantee the independence of the special prosecutor. Second, he wrote that Cox was being required to accept less than he had won in two court decisions. "While Cox has rejected a proposal I consider reasonable, his rejection of it cannot be regarded" as grounds for his removal. The next morning Richardson planned to make that clear to the president.

But that night, Nixon was drawing his own red lines. Even if Richardson was on his side, the Stennis deal was not sufficient if it didn't block future demands for tapes. Buzhardt wanted him to leave it alone -- the Stennis compromise for now would be a giant step toward the end of Watergate.

Eventually, Nixon blew up at him. "No," the president said. "No, period!"

Buzhardt had been sure he could maneuver Cox into a position where the special prosecutor would have to resign, since the White House and Richardson would be lined up against him. But to do it, he needed some negotiating room. The president had just denied him exactly that. By asserting that the special prosecutor could not subpoena additional evidence, they were laying credible grounds for Cox's defiance -- instead of his resignation. And they were probably throwing Richardson into Cox's arms. Now a showdown was inevitable.

• • •

Early the next morning, Friday, October 19, Richardson had "Why I Must Resign" typed and put it in his pocket. He called Haig and asked to see the president. But when Richardson arrived at about 10 a.m., Haig had a new deal. "Suppose we go ahead with the Stennis plan without firing Cox," he said. Instead, they would persuade the appeals court to accept the transcripts instead of the tapes, allowing use of the Stennis compromise without Cox's assent. Perhaps the Senate Watergate Committee would also accept transcripts.

Richardson was taken aback. That would be fine, he said, thinking to himself that he wouldn't have to resign, either. Haig said he would try to persuade the president.

Richardson was in for another surprise when he learned at the meeting that White House lawyers had asked Cox "not to subpoena any other White House tape, paper or document." Obviously, the special prosecutor could not accept that, and this had not been part of the proposal Richardson had submitted to Cox. Buzhardt said the president had forced them to add this new condition the previous night.

Haig left his office and came back soon to announce that Nixon had agreed to keep Cox. It had been "bloody, bloody," Haig said. "I pushed so hard that my usefulness to the president may be over."

Richardson tried to add things up in his own mind. The Stennis compromise had a new element: no future access. He was willing to accept it -- barely. Cox could resign or keep his job, as he chose, and Richardson would not have to fire him. Negotiations could continue. Richardson's reasons for quitting, neatly typed, stayed folded in his pocket. Now Haig thought he had Richardson on board.

Buzhardt said that the next problem was how to contain Cox. Couldn't Richardson simply order him not to go to court again for tapes? Cox would probably resign, but nobody appeared particularly concerned by that prospect. Richardson left the meeting, sure that there would be further discussion before any such orders were issued to Cox.

Back at his office, Richardson reviewed the White House meeting with his aides. They had expected him to resign, and they were not convinced that he could permit a restriction on Cox's future access without violating his agreement with the Senate. So Richardson called back Haig and then Buzhardt, insisting that the question of future access must not be linked to the Stennis plan. They promised to take up the question with the president again. Richardson relaxed, sure that he had avoided the immediate bind.

But the president was immovable. Whatever solution was arrived at, it had to solve the problem of the tapes once and for all, he told Buzhardt and Haig.

At 7 p.m., Haig called Richardson to read him a letter from the president that, he said, was on its way to him: "I am instructing you to direct Special Prosecutor Archibald Cox of the Watergate Special Prosecution Force that he is to make no further attempts by judicial process to obtain tapes, notes or memoranda of Presidential conversations."

Richardson was distressed that he had not been consulted. Haig said he had done his best. He had twice tried to make Richardson's position clear to the president. He had failed. Richardson took care to avoid saying whether he would issue the order.

But after Haig hung up, Nixon aides decided to announce the order through a White House news release, thus eliminating Richardson as intermediary. The order, in the president's name, was made directly to Cox, "as an employee of the executive branch."

This was too much for Richardson. "I will not do what the White House asks of me," he told another Nixon aide. "I've never been so shabbily treated in my life." He began drawing up his own press statement.

Haig called him and persuaded him to calm down. Prominent members of both parties were favorably disposed toward the compromise, he pointed out.

Richardson let one more opportunity for confrontation pass. He did not like bloodletting. He thanked Haig for his call. Richardson had negotiated Agnew's resignation, and he felt he could once again avert a national trauma.

But Cox was now faced with an order from the president to abstain from seeking more tapes. In fact, Cox was getting no tapes -- merely transcripts. He reasoned that he had the court, the law and the attorney general on his side. He announced that he would have a news conference early the next afternoon, Saturday, October 20.

Buzhardt expected Cox would announce his resignation. That will be tough, he thought to himself, but the president can weather it. Yet when Cox stepped before the cameras, he said he would continue pressing in court for the tapes. He might be compelled to ask that Nixon be held in contempt if the White House refused to turn them over.

Still, Cox acknowledged the obvious: "Now, eventually a president can always work his will," he said. "You remember when Andrew Jackson wanted to take the deposits from the Bank of the United States and his secretary of the treasury wouldn't do it. He fired him and then he appointed a new secretary of the treasury, and he wouldn't do it, and he fired him. And finally he got a third who would. That's one way of proceeding."

• • •

To Nixon, this was the ultimate defiance. He had issued a clear order to Cox, who was an employee of the executive branch. The president needed to show that he was in control. He told Haig to have Cox fired.

Haig called Richardson and ordered him to fire Cox. He was pretty sure Richardson wouldn't do it. As expected, Richardson replied that he wanted to see the president, to submit his resignation. In the midafternoon he went to the White House, and Haig started working him over: He must not resign now. Fire Cox, wait a week, and then resign.

"What do you want me to do," Richardson asked sarcastically, "write a letter of resignation, get it notarized to prove I wrote it today, and let it surface in a week?"

"That's not a bad idea," Haig replied matter-of-factly.

"I want to see the president," Richardson said.

He walked into the Oval Office at 4:30 p.m., and immediately Nixon urged him to delay. Nixon knew that firing Cox would invite a move to impeach.

Richardson said he could not. He was thinking to himself that this was the worst moment in all his years of service in government. He was standing there, refusing an urgent demand of the president of the United States. He had considered himself a team player.

"I'm sorry you feel that you have to act on your commitment to Cox and his independence," the president said, "and not the larger public interest."

There was a flash of anger. "Maybe," Richardson replied hotly, "your perception and my perception of the public interest differ."

That was the end.

Deputy Attorney General William D. Ruckelshaus was now the acting attorney general. Haig phoned him, painting a picture of cataclysm if Ruckelshaus did not fire Cox. "As you probably know," he said, "Elliot Richardson feels he cannot execute the orders of the President."

"That is right, I know that."

"Are you prepared to do so?"

"No."

"Well, you know what it means when an order comes down from the commander in chief and a member of his team cannot execute it."

"That is right."

Haig thought Ruckelshaus was fired. Ruckelshaus presumed he had resigned.

At about 6 p.m., Solicitor General Robert Bork, the third in command at the Justice Department, accepted the order and signed the White House draft of a two-paragraph letter firing Cox. At 8:22 p.m., White House press secretary Ron Ziegler announced this news, adding that, further, "the office of the Watergate Special Prosecution Force has been abolished as of approximately 8 p.m."

After 9 p.m., Haig sent FBI officers to seal off the offices of Richardson, Ruckelshaus and Cox to prevent any files from being removed.

The television networks offered hourlong specials. The newspapers carried banner headlines. Within two days, 150,000 telegrams had arrived in the capital, the largest concentrated volume in the history of Western Union. Deans of the most prestigious law schools in the country demanded that Congress commence an impeachment inquiry.

By the following Tuesday, 44 separate Watergate-related bills had been introduced in the House. Twenty-two called for an impeachment investigation.

• • •

Soon thereafter, Nixon made two fateful miscalculations: He appointed another special prosecutor to replace Cox, and he turned over an initial batch of tapes, including one that vividly incriminated him. The Trump-Mueller history is yet to be written.