Considerable mythology has arisen about Watergate, and these myths are confusing the current discussion around why and how Nixon was driven from office—which in turn has muddled the conversation around the possible fate of Donald Trump, whom Democrats might move to impeach if they take control of the House in November. In any event, it’s worth separating myth from reality when it comes to Watergate and the impeachment proceedings against Richard Nixon.

One of the greatest misconceptions around Watergate is that it was the break-in at the headquarters of the Democratic National Committee, and the subsequent cover-up, that led to Nixon being forced to surrender the presidency. But, in fact, when Nixon returned to Washington from his vacation home in Key Biscayne, Florida, three days after the break-in had been discovered, he and chief of staff H.R. Haldeman had another matter on their minds. The two men were worried that if the burglars—a group of “plumbers,” established ostensibly to ferret out the source of leaks that upset the Nixon White House led by E. Howard Hunt, a former C.I.A. operative who’d participated in the Bay of Pigs invasion, and G. Gordon Liddy, a former F.B.I. G-man—talked to federal investigators, their other activities on behalf of the White House might come to light. The real role of the plumbers was to “destroy” (Nixon talked that way) Nixon’s real and perceived “enemies,” meaning that, as Haldeman put it to the president when they met three days after the discovered break-in, “the problem is that there are all kinds of other involvements.” (This conversation was recorded on the tape of which 18 and a half minutes was later discovered to have been erased—a revelation that set off one of a number of explosions in the Watergate story. John Ehrlichman, Nixon’s head of domestic policy, wrote in his memoir that Nixon had done the erasing at Camp David.)

The “other involvement” that Nixon and Haldeman were most worried about being discovered was a break-in on September 3, 1971, more than nine months before the famous Watergate intrusion. This earlier break-in occurred at the office of the psychiatrist of Daniel Ellsberg, the defense analyst who, in June 1971, leaked the Pentagon Papers, a Johnson-era analysis of the Vietnam War, to The New York Times, The Washington Post, and The Boston Globe. Although the report had nothing to do with the Nixon administration directly, it did raise serious questions about the rationale for the war. Nixon, egged on by national-security adviser Henry Kissinger, was enraged at the study’s leak, and wanted Ellsberg “crushed” and any further unfortunate leaks stopped. And so the Office of Special Investigations—the plumbers unit—was established, and Nixon’s obliging top aides drew up “Hunt/Liddy Special Project No. 1,” the goal of which was to recover damaging intel on Ellsberg.

Once it was revealed, the break-in at the office of Dr. Lewis Fielding was considered by observers—as it had been by Nixon himself—to be far more serious than the Watergate break-in. Even conservative members of Congress were shocked. During hearings by a special Senate committee in the summer of 1973, Georgia’s conservative Democratic Senator Herman Talmadge (southern Democrats hadn’t yet gone red) asked Ehrlichman if he recalled the English principle in which “no matter how humble a man’s cottage is, even the king of England cannot enter without his consent.” Ehrlichman replied chillingly, “I am afraid that that has been considerably eroded over the years.”

As it happens, the burglars found no medical papers about Ellsberg in Dr. Fielding’s files. Nevertheless, that particular raid had far-reaching consequences. It remained secret until Ellsberg’s 1973 trial, when the Justice Department was obliged to disclose it. Citing this stunning news, the presiding judge dismissed the case against Ellsberg, saying that the administration’s behavior “offend[s] a sense of justice.” The Fielding break-in was incorporated into the articles of impeachment against Nixon.