Donald Trump recently told crowds a story about U.S. Gen. John Pershing executing Muslim insurgents with bullets dipped in pig’s blood. It’s a gruesome story, and it is also not true. But it does point to a real, complicated history about the United States’ involvement in the Philippines during the early 1900s.

Speaking in South Carolina ahead of the primary, Trump told his crowd that Pershing, who led U.S. troops during World War I, was a “rough guy,” according to Mother Jones. He then said that during the Moro rebellion in the Philippines (1899-1913, and Pershing served as governor of the Moro Province between 1909 and 1913), Pershing “caught 50 terrorists who did tremendous damage … and he took the 50 terrorists and he took 50 men and dipped 50 bullets in pig’s blood. You heard about that? He took 50 bullets and dipped them in pig’s blood. And he has his men load up their rifles and he lined up the 50 people and they shot 49 of those people. And the 50th person, he said, you go back to your people and you tell them what happened.”

For Muslims, ingesting pork is a sin, and pig’s blood is considered unholy.

Brian McAllister Linn, a history professor at Texas A&M University who is an expert in the Philippine conflict, said he first remembers this tale about Pershing surfacing right after the terrorist attacks on September 11, 2001. (Another version of the story has Pershing burying Muslim bodies with pigs.) Linn said that he and Frank Vandiver, who wrote a biography of Pershing and passed away in 2005, were contacted at the time about the veracity of the story.

“We both checked our notes and found no evidence to support this,” Linn told TIME. “We also concluded it was out of character.”

Snopes, a myth-busting site, came to the same conclusion: “We haven’t yet found any references to this alleged incident in Pershing biographies, however, nor does it match the way Pershing is generally recorded as having dealt with the Moros in 1911,” the site concludes.

It may have been out of character for Pershing, but it may not have been out of character for other U.S. troops. Trump did hit on an unfortunate truth that the occupation of the Philippines involved deliberate attempts—at least among the ranks—to use religious taboos to intimidate people.

In 1941, TIME ran a letter to the editor from a soldier named J. R. McKey who had served with Pershing in the Philippines decades before. In the letter, McKey describes using pigs in burials to deter Muslim insurgent activities, but does not ascribe the act to Pershing.

McKey wrote, “U.S. soldiers … had a pretty good cure for juramentado [Moro swordsmen] activities. Knowing the horror of the Mohammedan for any contact with swine, and particularly with its blood, these American roughnecks, when they had killed a juramentado, held for him a very public funeral. The body of the defunct bad man having been deposited in the grave, a pig was brought, stuck, its blood sprinkled freely over the D B M, the dead pig thrown in with him, and the burial completed.”

Some reports do say that Pershing was engaged in burying Muslims with pigs or throwing pig’s blood on them. According to the History News Network, a Chicago Daily Tribune article from 1927 describes Pershing sprinkling prisoners with pig’s blood, then setting them free to warn others of being doused with the blood. “Those drops of porcine gore proved more powerful than bullets,” the article wrote.

Christopher Capozzola, a history professor at Massachusetts Institute of Technology, also cited an incident in which Pershing brought a pig’s head to a ceasefire negotiation with a Muslim leader.

“So yes, there were deliberate efforts to offend Muslim Filipinos’ religious sensibilities,” Capozzola told TIME. “And yes, there was large-scale violence against their communities. But I know of no event like the one that Mr. Trump describes.”

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Write to Tessa Berenson at tessa.berenson@time.com.