From 9 a.m. to 5:45 p.m. Tuesday, morality and conscience did quiet battle with protocol and budgets in Courtroom 1A of U.S. District Court, to which dozens of supporters marched that morning through downtown Knoxville, led by two Buddhist monks chanting a Japanese prayer for peace.

Megan Rice, an 83-year-old Catholic nun currently living in the District, and two of her fellow peace activists faced the first day of their trial here on charges that they intended to injure the national defense when they intruded into the Y-12 National Security Complex in Oak Ridge, Tenn., in the pre-dawn hours of July 28, 2012.

In front of a courtroom filled with activists and supporters — and via a closed-circuit television in an overflow court — lawyers for the defense and the government essentially agreed on what happened July 28 but diverged on what the uncontested evidence proved. The intrusion — which involved hiking over a ridge, cutting through four chain-link fences and vandalizing the exterior of a warehouse holding highly enriched uranium — shut down operations for about two weeks at Y-12, a nuclear weapons production facility 30 minutes west of Knoxville.

“Their whole purpose was to interfere or obstruct Y-12 operations,” said Assistant U.S. Attorney Melissa M. Kirby in her opening statement to the jury of 10 men and four women (two jurors are alternates).

“They had white roses, Bibles . . . no dynamite, no machine guns . . . none of the tools you’d anticipate someone having to hinder the national defense,” countered Christopher Irwin, attorney for co-defendant Michael Walli, a Vietnam War veteran who lives at the Dorothy Day Catholic Worker house in the District.

Walli, Rice and Greg Boertje-Obed of Duluth, Minn., are also charged with causing damage in excess of $1,000 at Y-12, a contractor-run government facility that stores and processes highly enriched uranium, a radioactive fuel for nuclear weapons. Together, the two felonies carry a maximum sentence of 30 years in prison. The three anti-nuclear activists say they violated the law to call attention to the possession and maintenance of nuclear weaponry, which they consider a greater injustice, and are therefore not guilty.

“We believe the work at Y-12 contributes to false security,” Boertje-Obed, who is representing himself, said in his opening statement. “Nuclear weapons are an illusion of security. . . . Our message, our mission, is we need to transform the U.S. role in the world.”

Boertje-Obed told the jurors that they are “the conscience of the community” and ended his statement by quoting the Book of Hebrews: “If today you hear God’s voice, harden not your hearts.”

On the first day of the trial, the prosecution tabulated the physical damage to the site and argued that the 15-day suspension of operations delayed the site’s production schedule and damaged the credibility of the U.S. “nuclear deterrent” — which is tantamount to obstructing the national defense.

“All our allies, enemies and citizens understand that nuclear weapons are here and will work if needed,” testified Steven Erhart, the top official in Oak Ridge for the National Nuclear Security Administration, the semiautonomous agency in the Energy Department that secures and manages the nation’s stockpile.

“The primary mission of Y-12 is to support the nuclear deterrent and national security,” said Erhart, who added that “without Y-12 we don’t have a nuclear weapon” and that obstructed weapons programs “lessen our security.”

The defense sought to minimize the threat posed by the defendants’ actions, which were intended to be symbolic but necessitated at least $8,531.67 in physical repairs and associated labor, according to the government.

At certain points, both the defense and the prosecution litigated the final actions of World War II.

You’d agree that the bombs dropped on “Hiroshima and Nagasaki killed tens of thousands?” William Quigley, Walli’s pro-bono attorney, asked Erhart.

“Yes, sir,” Erhart replied.

“The same thing would happen if they were dropped on a civilian center here,” said Quigley, attempting to set his client’s actions against an infinitely more destructive hypothetical.

“If used in that manner, yes, sir,” Erhart said

After a lunch break, Assistant U.S. Attorney Kirby asked Erhart: “What event ended World War II?”

“The events we talked about earlier,” Erhart said. “The bombings of Hiroshima and Nagasaki.”

“And how many American lives were saved” by those events? Kirby asked, prompting critical murmurs from the courtroom audience.

“I’ve heard — ”

“Objection,” said Francis Lloyd Jr., attorney for Sister Megan. “Speculation.”

Judge Amul R. Thapar upheld the objection and otherwise tried to keep the proceedings from swaying too much between historical tangents and such opaque phrases as “normalization of a deviation from the optimum,” used by Erhart to describe how Y-12’s high rate of false alarms contributed to the July 28 breach.

The government showed the jury the grainy black-and-white surveillance video of the intrusion and called to the stand Kirk Garland, the protective-force officer who was the first to respond to the intrusion.

“Were they passive?” asked Irwin, trying to establish that the defendants did not have sabotage in mind, during cross-examination.

“They were passive,” Garland said.

The government also played audio of all three defendants admitting to their actions during recorded telephone calls from the Blount County jail.

The defense opened its case at 4:45 p.m. by calling Rice to the stand. Lloyd inquired about her upbringing on the Upper West Side of Manhattan, her education on the topic of nuclear weapons, her 40 years of building classrooms and teaching in Africa.

Wearing a purple fleece jacket and a T-shirt imprinted with “I wish to live without war,” Rice said that her uncle, a Marine sent to Nagasaki six weeks after the bomb was dropped in 1945, told her of the devastation of the city. She said she went on to study cellular biology and radioactivity at Boston College and Harvard Medical School, where during experiments she wore a lead vest with her black habit.

When Lloyd asked about the damage they caused at Y-12, the nun shrugged.

“I could’ve repaired it,” she said.

A verdict is expected by Friday. The cross-examination of Sister Megan Rice begins Wednesday morning.