College Park, Md. ? Thinking big, President Nixon raised the idea of using a nuclear bomb against North Vietnam in 1972, but Henry Kissinger quickly dismissed the notion.

“I’d rather use the nuclear bomb,” Nixon told Kissinger, his national security adviser, a few weeks before he ordered a major escalation of the Vietnam War.

“That, I think, would just be too much,” Kissinger replied softly in his baritone voice, in a conversation uncovered among 500 hours of Nixon tapes released Thursday.

Nixon responded matter-of-factly. “The nuclear bomb. Does that bother you?” he asked. Then he closed the subject by telling Kissinger: “I just want you to think big.”

He also said “I don’t give a damn” about civilians killed by U.S. bombing.

That exchange in the Executive Office Building on April 25, 1972, is contained in the largest batch of tapes ever released by the National Archives. Altogether, roughly 1,700 of the 3,700 hours of Nixon White House tapes have now come out.

Most of the newly released tapes were recorded between January and June 1972.

They offer insights into Nixon’s historic trip to China in February of that year and the mating habits of two pandas he received as a gift.

“The only way they learn how is to watch other pandas mate, you see,” Nixon said in a phone conversation with a columnist for The Washington Star.

In June 1972, Nixon and chief of staff H.R. Haldeman can be heard worrying about the erratic behavior late-night telephone calls to reporters, for instance of Martha Mitchell, the outspoken wife of campaign manager John Mitchell. She had complained about political dirty tricks.

“The woman is sick,” Nixon said.

Nixon and his aides are heard talking over ways to limit the fallout if the White House is implicated in the break-in at the Democratic National Committee at the Watergate. The plan: Blame John Mitchell, saying he was so busy trying to control his wife that he was not minding the campaign.

Other Watergate-related tapes include the infamous 18 1/2 minute gap, an erased segment three days after the break-in. The gap a series of whirs, clicks and buzzes was released in the 1970s. But the poor quality of the tape makes conversations before and after the gap unintelligible, too.

Facing re-election in 1972, Nixon worries aloud on one tape that if America lost the Vietnam War and the Soviets pulled out of a coming arms-control summit, his political career would be history. He says he would pull out of the presidential race and back former Texas Gov. John Connally for the GOP nomination.

He told Kissinger, “The point is, we have to realize that if we lose Vietnam and the summit, there’s no way that the election can be saved.”

The summit was not canceled, and soon Nixon was escalating the war. The president signed arms agreements with the Soviets in Moscow and tried to pin the blame for the assassination attempt against George Wallace on liberals in an effort to boost his own political prospects.

After hearing of the shooting, Nixon asked about Wallace’s health and made sure other presidential candidates were adequately protected. Then he turned to using the incident for political advantage.

Within hours of the shooting, Nixon is heard on the tapes stirring up rumors that the suspect, Arthur Bremer, was a left-winger with connections to the Kennedys.

Nixon can be heard on one tape whispering the rumors in the background as his adviser Chuck Colson, on the phone with the FBI’s Mark Felt, passes on that Bremer and his associates might be “Kennedy friends.”

“I’ll be sure and pass that along,” Felt says.

The war weighed heavily on Nixon’s mind.

“We can’t lose 50,000 Americans and lose this war,” Nixon told comedian Bob Hope on April 15.

Nixon’s thoughts about the nuclear bomb could have reflected mere frustration with the war or been part of a strategy to make the North Vietnamese believe he was a madman and could not be restrained and so they should negotiate peace.

“It was politically unacceptable,” Vietnam historian Stanley Karnow said of the prospects of using the bomb. “Just because he said it doesn’t mean it was really an option.”

The tapes are replete with Nixon blurting out outlandish remarks, said Nixon historian Stanley Kutler, who clamped on earphones to listen to the tapes at the archives complex outside Washington.

“It’s a frustrated, angry, confused president lashing out and calling on what he had access to, to defeat an intractable enemy,” Kutler said, adding that he believed Nixon was not serious about dropping the bomb.

In May, Nixon reminds Kissinger that civilians are an unfortunate casualty of all wars.

“The only place where you and I disagree … is with regard to the bombing,” Nixon said. “You’re so goddamned concerned about the civilians and I don’t give a damn. I don’t care.”

“I’m concerned about the civilians because I don’t want the world to be mobilized against you as a butcher,” Kissinger said. “We can do it without killing civilians.”