After a terrorist deliberately crashed a van into a crowd of people in Barcelona on Aug. 17, President Donald Trump took to Twitter to condemn the attack. He then suggested that the world should get tougher on terrorism.

"The United States condemns the terror attack in Barcelona, Spain, and will do whatever is necessary to help. Be tough & strong, we love you!," Trump tweeted.

He later followed up, writing: "Study what General Pershing of the United States did to terrorists when caught. There was no more Radical Islamic Terror for 35 years!"

The person who needs a lesson, however, is Trump.

Trump has made this claim about U.S. Army Gen. John Joseph "Black Jack" Pershing before. During a Feb. 19, 2016, rally in North Charleston, S.C., Trump referred to an anecdote from the aftermath of the Philippine-American War of 1899-1902, when the United States sought to exert its authority over the Asian archipelago, which it had recently obtained from Spain after winning the Spanish-American War.

After taking the reins of power from Spain, the United States faced armed opposition, and the three-year war led to the deaths of more than 4,200 American combatants, more than 20,000 Filipino combatants, and as many as 200,000 Filipino civilians, according to the State Department.

After the war, Pershing served as governor of the heavily Muslim Moro Province between 1909 and 1913. This period was notable for its continuing insurgencies.

"They were having terrorism problems, just like we do," Trump said, according to a February 2016 account in the Washington Post. "And he caught 50 terrorists who did tremendous damage and killed many people. And he took the 50 terrorists, and he took 50 men and he dipped 50 bullets in pigs’ blood — you heard that, right? He took 50 bullets, and he dipped them in pigs’ blood. And he had his men load his 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. And for 25 years, there wasn’t a problem. Okay? Twenty-five years, there wasn’t a problem."

In Trump’s most-recent telling, 25 years became 35 years.

But either way, neither version of the story adds up.

Did it happen?

The idea that pig’s blood could serve as a weapon against Muslims has been around in popular culture for decades.

For instance, a 1939 Hollywood movie, The Real Glory, stars Gary Cooper as a doctor on the Philippine island of Mindanao who drapes a captive in pigskin "to serve as an abject lesson to all would-be attackers," Luis H. Francia, a Filipino-born professor of Asian American Studies at Hunter College, wrote recently.

The best evidence U.S. troops used pigs as a tactic against Muslims comes from a memoir by Pershing titled My Life Before the World War, 1860-1917, which was republished in 2013 by the University Press of Kentucky. In the memoir, Pershing writes that another commanding officer in the Philippines, Col. Frank West, had in at least one case seen to it that bodies of Muslim insurgents "were publicly buried in the same grave with a dead pig. It was not pleasant to have to take such measures, but the prospect of going to hell instead of heaven sometimes deterred the would-be assassins."

In a footnote, the editor of the 2013 edition, John T. Greenwood, cited a letter about the incident from Maj. Gen. J. Franklin Bell, the commander of the Philippines Division, to Pershing: "Of course there is nothing to be done, but I understand it has long been a custom to bury (insurgents) with pigs when they kill Americans. I think this a good plan, for if anything will discourage the (insurgents) it is the prospect of going to hell instead of to heaven. You can rely on me to stand by you in maintaining this custom. It is the only possible thing we can do to discourage crazy fanatics."

While these writings do provide strong evidence that United States forces used pigs as a tactic against Muslim insurgents, there is no evidence that Pershing himself committed these acts.

Experts have been skeptical the practice was widespread or directly authorized or ordered by Pershing.

"This story is a fabrication and has long been discredited," said Brian McAllister Linn, a Texas A&M University historian and author of Guardians of Empire: The U.S. Army and the Pacific, 1902-1940. "I am amazed it is still making the rounds."

Christopher Einolf, a professor at DePaul University and author of America in the Philippines, 1899-1902: The First Torture Scandal, added that he trusted the conclusion of the late military historian Frank E. Vandiver, who told About.com in 2003 that "I never found any indication that it was true in extensive research on his Moro experiences. This kind of thing would have run completely against his character."

Indeed, other historians noted that Pershing pursued a less brutal approach to "pacifying" the rebels in the southern Philippines than Leonard Wood, one of his predecessors.

"He did a lot of what we would call ‘winning hearts and minds’ and embraced reforms which helped end their resistance," said Lance Janda, a military historian at Cameron University. "He fought too, but only when he had to, and only against tribes or bands that just wouldn’t negotiate with him. He wasn’t solely committed to fighting as people like Trump who tell the pig blood story imply."

Another wrinkle: Historians said the premise that the rebels would have been motivated by a fear of pigs is not as certain as Trump suggests. It’s unclear how religiously observant the insurgents were and whether such a policy would have made a difference in their actions.

"The Moros were fighting for a lot of reasons, not just because they were Muslims," Janda said. "This is another fact that gets lost in many modern discussions of terrorism."

Details aside, Trump’s point about terrorism is wrong

To many of the historians we checked with, the idea that Pershing’s actions stopped "radical Islamic terror" was actually the bigger problem with Trump’s parable.

"Even if the tale is true, the pacifying effect that Trump claims is nonsense," said Michael H. Hunt, an emeritus historian at the University of North Carolina and author of Arc of Empire: America's Wars in Asia from the Philippines to Vietnam. The region "remained in constant unrest during the period of American rule and into the period of independence, right down to the present."

Silbey of Cornell agreed. "Where Trump’s remark becomes ridiculous is in the idea that this actually worked," he said. "The Moro War did not end until 1913, and even that’s a bit of a soft date, with violence continuing for quite a while afterward. Defilement by pig’s blood isn’t -- and wasn’t -- some magical method of ending terrorism."

If anything, a more complete account of the Moro insurgency involves some subplots that run contrary to Trump’s narrative.

"The Ottomans under Sultan Abdul Hamid II sent a letter to the Sulu Moros asking them not to resist the Americans at the start of the Moro Rebellion, and the Moros on Sulu complied," Janda said. "It’s a nice example of diplomacy working to our advantage, and a reminder that then and now, not all Muslims or Moros are the same and that many were and are U.S. allies."

Our ruling

Trump said that Pershing stopped "radical Islamic terror" for 35 years. Of the eight historians we checked with the first time we heard Trump speak about Pershing, all were at least skeptical that the specific tales of Pershing actually took place, and some expressed disbelief even more forcefully than that.

But more critically, the historians took issue with Trump’s suggestion that the tactic -- if it was even used at all -- actually worked to end tensions, noting that unrest persisted for years. Trump’s claim rates Pants on Fire.