It was called, simply, “the Terror.”

It was probably the closest Western Europe ever came to the horrors of Rwanda — not just in body count, but as mere anarchy loosed upon the world.

It was the French Revolution, and from September 1793 to July 1794, nearly 2,000 people a month were beheaded in Paris, many for nothing more than being too tepid in support of the Revolution.

And in the middle of this bloody storm was painter Jacques-Louis David, who created the most famous painting of the Revolution, The Death of Marat, in 1793. It was a masterpiece of political propaganda.

But that is not all David did for the Revolution: That is not red paint on the artist’s hands. The painter personally signed at least 300 death warrants as a member of the Jacobin government’s Committee for General Security.

The painting, originally called Marat at His Last Breath, created a martyr of the revolution from a man who is more properly a war criminal. And it again raises the question of art’s moral responsibility.

The dead man in the painting, Jean-Paul Marat, was a journalist who called for thousands of heads to roll. “No, hundreds of thousands,” he wrote.

And on July 13, 1793 — the day before what is now Bastille Day — this greatest, most bloodthirsty exponent of the Terror was stabbed to death by a young woman.

“I killed one man to save a hundred thousand others,” she said.

She miscalculated. She had killed Jean-Paul Marat, but his death unleashed the worst of the Terror.

Jean-Paul Marat was not the kind of person you would think of if you wanted to create a hero.

He was a peculiar man, formerly a physician — some called him a quack — and at turns vicious and paranoid. He cut an unpossessing figure: Ugly, short, he suffered from a skin disease, likely a psoriatic arthritis, that left his face scarred: He called it “leprous.” To salve his discomfort, he conducted his daily business from a bathtub filled with cool water. On his head he wore a towel soaked in vinegar for relief. A board across the tub provided a desk.

Marat published a newspaper called Friend of the People, which harangued and incited. He lauded what he considered republican virtue and selflessness, and called for the death of anyone he considered a traitor: that is, anyone who didn’t agree with him. Patriotism and selfless devotion to the cause drove Marat.

It went well beyond a call for the beheading of the aristocracy.

In fact, during the Terror, 70 percent of those killed were from the lower classes. People settled grudges by informing on their neighbors. An accusation was enough.

But for painter Jacques-Louis David, Marat became the perfect subject to deify when he was assassinated in the early months of the “Reign of Terror.”

His assassin, Charlotte Corday, then just 23, felt just as keen a patriotism as Marat. But for her, patriotic duty meant she must kill “the monster, Marat,” even if it meant her own death.

She came to Paris, bought a 6-inch kitchen knife, wrote a note explaining her actions and pinned it to the inside of her dress. In it she called Marat “the savage beast fattened on the blood of Frenchmen.” She also bought a new hat, a green one.

On the morning of July 13, 1793, she went to Marat’s apartment, armed and determined. She couldn’t get past Marat’s bodyguards. But she came back in the evening, slipped in behind some delivery men, flashed a phony list of the names of “traitors.” Marat showed interest, calling her to his tub.

Marat looked the list over and told her, “Don’t worry, in a few days I will have them all guillotined at Paris.”

She then pulled out the knife and stabbed him in the chest once, severing his aorta and puncturing a lung. A jet of blood sprayed the room. He died calling for help from his friends.

Four days later Corday was beheaded for her crime, and Marat was transformed into a patriotic martyr.

And David was just the man to do it. He had been the artist of the Revolution, creating images of republican virtue and the glorious past.

When the news of Marat’s death reached the National Convention, one delegate yelled out, “David, where are you? Take up your brush — there is yet one more painting for you to make.”

The propaganda machine went into high gear. A great public funeral was held — organized by David — streets were renamed for Marat, poems and songs were written. At least one new restaurant opened in the rue Saint-Honore called the Grand Marat.

“Indeed, Marat dead was perhaps more useful to the Jacobins than the unpredictable, choleric live politician,” wrote Simon Schama in Citizens, his history of the French Revolution.

A commission for a painting was voted and David began three months’ work on what would be seen as his masterpiece.

When it was finished, it was paraded around Paris like a Mexican santo, rallying the people to redouble their republican ardor and sharpen the cleansing edge of the guillotine’s blade.

Thousands of cheap engravings were distributed, made from a death-mask portrait drawn by David. Marat’s eyes closed, his head tilted in death.

Copies of the painting were ordered from David and his atelier, to be sent to the other cities of France.

Instead of stopping the violence, as Corday had hoped, her act only worsened the Terror. The assassination now became a cause.

As for David, when the Terror ultimately collapsed and its architect, Maximilien Robespierre, was guillotined, the painter went to prison. At least he kept his head.

He was released after about a year in a general amnesty.

When Napoleon came to power, David became the imperial artist, glamorizing the First Consul as he had glamorized the Revolution. David was a political chameleon, a slippery eel. The artist was always looking for a “great man” to glorify, whether it was Marat or Napoleon.

When Napoleon fell, David went into exile in Belgium, where he died in 1825.

His great painting had a similar fate: It was withdrawn from the public shortly after the fall of Robespierre and sent back to the artist’s studio, where it remained, unexhibited till well after David’s death.

Finally, in 1848, republican sentiment arose once more in France and Marat came out of storage. The poet Charles Baudelaire saw it and wrote a famous encomium, which raised public awareness of the masterpiece once more. The painting became canonized.

Today, the most recognized souvenir of Marat’s life and death is the painting David made to immortalize the journalist.

It is powerful: “David weaponizes art,” said one museum curator.

David’s painting is hugely original, mixing an almost journalistic sense of the here and now with familiar iconographic symbols, like the hanging arm of Michelangelo’s Pieta, turning the dying journalist into a Christ figure.

That isn’t just a conceit: The subconscious reading of the painting can’t help seeing the echoes of earlier, religious paintings. David was able to mythologize current events and give them depth and power.

“If there’s ever a picture that would make you want to die for a cause, it is Jacques-Louis David’s Death of Marat,” historian Simon Schama says in his TV series The Power of Art. “That’s what makes it so dangerous — hidden from view for so many years. I’m not sure how I feel about this painting, except deeply conflicted. You can’t doubt that it’s a solid-gold masterpiece, but that’s to separate it from the appalling moment of its creation, the French Revolution.

“If ever a work of art says that beauty can be lethal, it’s Jacques-Louis David’s Marat.”

David has turned the paranoid fanatic into a saint of the revolution. He had also made what some have called the first “modern” painting: spare, direct, almost abstract in its design.

But the image raises a question: Can great art be made for evil reasons?

The question is not merely academic. These questions have come up many times in the past: Can Leni Riefenstahl be a great filmmaker if the films she made glorify Hitler? Can D.W. Griffith’s Birth of a Nation really be one of the most important films ever made if its heroes are the Ku Klux Klan?

And what about Westerns? Are our heroes cowboys? Or do we acknowledge our own genocide? What was once the patriotic foundation myth of our nation now embarrasses any thoughtful American. The once-famous Battle of Wounded Knee has now become the Massacre at Wounded Knee.

So, what do we make of art when we question the artist’s motives?

There are some who believe composer Aaron Copland’s music can’t be any good because of his lefty political leanings. And the take people have on Shostakovich often depends on whether they see him as a Soviet apologist or a secret dissident.

The art of Englishman Damien Hirst horrifies some people, because he may use dead animals, pickled in formaldehyde, as part of his art. His shows bring out the picketers.

Wagner cannot be played in Israel because of his anti-Semitism and because Wagner was Hitler’s favorite composer. Where can we draw the line on this?

Do we ban politically injurious art, the way many would ban the use of Nazi medical research?

“I can appreciate pure ‘art for art’s sake,’ ” says artist Anne Coe, whose paintings are never politically neutral.

Coe is an ardent environmentalist and lover of animals, and her paintings promote her views.

“But to me, the really knock-your-socks-off art has a little more,” she says. “It has ideas behind it. I think art is insipid without some sort of idea in it.”

And David’s art is all about ideas.

“David is the artiste engage par exellence,” says Mary Morton, associate curator of paintings at the J. Paul Getty Museum. “He gave himself completely to politics.”

The subject of the painting, she points out, is not so much Marat the man but the virtues of republican self-sacrifice.

“David’s art is very didactic,” Morton says. “It is about civic responsibility.”

And perhaps we are removed enough from the events of 1793 that we can see in David’s painting the idea rather than the man — the spirit of democracy instead of the call for blood.

“What is that line between propaganda posters, like ‘Uncle Sam Wants You,’ and the David painting, or the paintings of religious martyrs?” Coe asks.

“Does some art lead to evil things? That is the risk you take in a society that says everything is relative.”

There is no single answer to the question; you have to take each case individually and weigh it in your own conscience.

“I listen to Wagner. I love Wagner,” Coe says. “You can’t have an answer.”