The bombs exploded at the finish line at 2:49 p.m. on April 15, 2013. The worst photos—the ones widely published on conspiracy websites—were taken during the immediate aftermath of the bombing: a woman sitting dazed in a pool of blood, her face smeared with grime; a man with both legs blown off, sliding around in a pool of his own viscera. One of his leg bones juts out, horribly white, pointing in the air like a mile marker. He’s looking away from the camera, off into the distance. In another shot, he’s being rushed toward medical aid in a wheelchair, what’s left of his legs visible.

“We were told his name is Jeff Bauman,” one conspiracy site wrote sarcastically soon after the bombing, referring to the man who had lost his legs. “But since that can’t be verified and his survival is unbelievable to the point of being miraculous, we’ll simply call him Miracle Man.”

The Boston Marathon bombings killed three people, including an eight-year-old boy who’d been cheering at the finish line, and injured more than two hundred, among them Bauman, who lost both legs above the knee. (His difficult road to recovery was documented in a memoir and a movie, and his name can most definitely be verified.)

The country was captivated by the manhunt that followed and the identification of the suspects as brothers Tamerlan and Dzhokhar Tsarnaev, two young Al-Qaeda sympathizers of Chechen descent. Four days after the marathon, Tamerlan, the older brother, died in a bizarre confrontation with police—he was first shot by officers and then run over by Dzhokhar attempting to escape. Dzhokhar was taken into custody alive and is today one of the youngest people on death row in the United States.

The story was gruesome, as dramatic as a Hollywood thriller, and its aftermath was filled with mysteries. Some have endured. It’s never been clear, for example, why an FBI agent shot and killed a friend of the Tsarnaev brothers during an interrogation at his apartment. (The agency claimed that the friend had a weapon; however, the agent who shot him had previous accusations of misconduct and assault. In 2017, the family of the victim sued two FBI agents and two Massachusetts state troopers.) Before the brothers were identified, before the strange killing of the friend—before any details were known—an alternate version had begun to play out, parallel to the official story, as the conspiracy community figured out what was really going on.

Conspiracy theorists converged on the Boston bombing within hours. One of the first questions at the initial press conference convened by the authorities following the bombings came from Dan Bidondi of InfoWars. Was the bombing, Bidondi demanded, “another false flag staged attack to take our civil liberties and promote homeland security while sticking their hands down our pants on the streets?”

“No,” replied Massachussetts governor Deval Patrick. “Next question.”

“Our hearts go out to those that are hurt or killed #Boston marathon,” Alex Jones tweeted, less than an hour after the bombs exploded. “But this thing stinks to high heaven. #falseflag.”

One of the most intense and immovable American fears is of subliminal, hidden government control. We’re also worried about the other, more overt kind—armies marching down the street, doors kicked in, guns in our faces—but the murky circumstances behind several major military conflicts, combined with revelations of various secret FBI and CIA programs, have helped foster the suspicion that we might be controlled and manipulated through more subtle means, ones beyond our recognition. That’s one reason for paranoia about such threats as mind-controlling fluoride in the water supply, subliminal messages in advertising and Disney movies, and brainwashing in schools through the Common Core curriculum. But the fear of invisible government manipulation is also largely accountable for the prevalence of theories of false flags: the idea that mass casualty events have been orchestrated or carried out by the government to consolidate its power.

In the years since 9/11, and intensifying after the 2012 shooting that killed twenty children and six adults at Sandy Hook Elementary School in Newtown, Connecticut, most major mass casualty incidents in the United States have been subject to accusations of having been staged by the government, done to keep an unsophisticated populace in line. The charges are always the same: the people supposedly wounded or killed are actors, the photos and videos of the event are doctored, the witnesses are paid government spooks. Each of these conspiracy theory–generating events creates months of television news coverage after the fact, along with mountains of photographic and video evidence. That evidence is dissected by “researchers,” as they call themselves, in a way that’s come to seem so familiar, it’s sometimes used for comedic effect: an interlocking system of red lines, arrows, textual notes, and geometric angles, overlaid atop the images like layers of a chaotic cake, pointing everywhere and at nothing simultaneously.

Though false flag theories spring up routinely around any event in which a lot of people die and that is covered heavily in the news, the accusation is especially common in response to mass shootings; conspiracy theorists, particularly on the far right, tend to link such shooting attacks to the liberal campaign for gun control.

Sometimes false flag theories dovetail with anti-Semitism and Islamophobia; attacks are frequently attributed to Israel or ISIS. That happened in the days following the Boston attack, when anti-Semitic conspiracy sites blamed Zionists, Israel, or simply the Jews at large. (“Zionist Jews Strike Again, Murdering Three in Boston,” a site called NoDisInfo blared.) Florida anti-Muslim pastor Terry Jones—best known for publicly burning a Quran—declared that Obama planned to cover up the crime in sympathy for his fellow Muslims. “Is it an Islamic attack? It looks like it,” he wrote in a statement. “The bombing came on Patriots Day. It has all of the earmarkings of an Islamic attack but will there again be a great coverup by the Great Satan Obama? His Administration, the people he has surrounded himself with, are all some type of closet Muslims, heavily influenced by Islam because of their background.”

The callousness of false flag researchers can be shocking and painful to witness, even when they’re not dipping into outright hate speech. In November 2017, a gunman stormed into a church in the small town of Sutherland Springs, Texas, and killed twenty-five people, one of them pregnant. The gunman had a long history of domestic violence, and his estranged wife sometimes attended the church he attacked. During the shooting, he murdered her grandmother. Yet the conspiracy theories sprang up immediately, most of them politically tinged: he was a Bernie Sanders supporter, a Hillary Clinton voter, an antifa (shorthand for “anti-fascist”) terrorist who claimed “this is a communist revolution” before murdering the parishioners. The killings were said to be an attack on Christianity itself: “Report: Texas church shooter was atheist, thought Christians ‘stupid,’” Breitbart’s headline blared.

In the months that followed, the church pastor, Frank Pomeroy, and his wife, Sherri, whose fourteen-year-old daughter, Annabelle, had died in the shooting, were viciously harassed, accused of participating in a staged Department of Homeland Security “drill” to frighten people into giving up their guns. One self-proclaimed journalist calling himself Side Thorn (real name Robert Ussery) took himself to Sutherland Springs with his partner Conspiracy Granny (real name Jodie Mann). They leaped out of their car and began berating Frank Pomeroy, who was sitting in his own car nearby. Ussery filmed the encounter.

“Your daughter never even existed,” he told Pomeroy. “Show me her birth certificate. Show me anything to say she was here.” The pair were arrested for trespassing and possession of marijuana, but Ussery declared the mission a partial success. “It was everything but an outright admission,” he wrote on his website.

There are examples throughout history of real or suspected false flag attacks; the name supposedly comes from a mode of pirate warfare, in which a pirate ship would feign distress to draw another vessel closer. When the other boat came within attacking distance, the pirates would raise their—surprise—black flag. The most infamous example cited is the 1933 Reichstag fire, in which the German parliament building was burned down. Hitler’s cabinet claimed the fire was the beginning of a communist putsch and moved to enact emergency laws; historians have long debated whether the arson was carried out by the Nazis themselves to consolidate power. The bombing of four Russian apartment buildings in 1999, which were blamed on Chechen militants, has been compared to the Reichstag fire: many believe the attacks were carried out by the FSB, the Russian security agency, to help Putin in his rise to the presidency.

In American history, the most heavily debated event as a possible false flag operation was the 1898 explosion and sinking of the USS Maine, an event that precipitated the start of the Spanish-American War. It’s never been clear whether the Maine was destroyed by an external explosion, as one government investigation found, or by a coal fire belowdeck, but the incident was blamed on Spanish forces, particularly in the tabloids of the day, and used as an incitement to war.

Justifying military involvement is a common theme in real or suspected false flags, and it cropped up in 1962’s infamous Operation Northwoods. A proposal from the Department of Defense and the Joint Chiefs of Staff, Northwoods baldly floated the idea that the CIA commit acts of terrorism against American citizens and blame them on Cuba to justify pushing a simmering conflict into a full-scale war. The attacks involved a riot outside Guantanamo, the US naval base in Cuba, as well as shooting down airplanes or setting off bombs in US cities. President Kennedy vetoed the operation, but just two years later, in the Gulf of Tonkin incident, American forces insisted they had been attacked twice by a North Vietnamese patrol boat. But the second attack never happened, as documents declassified years later showed. They also demonstrated that then Secretary of Defense Robert McNamara intentionally withheld evidence that might have led to a full investigation of the event and perhaps put a slight speed bump in the United States’ rush into the Vietnam War.

As with every conspiracy associated with the government, Northwoods opened the door to new conspiracy theories. In subsequent years, the false flags and abortive false flags of the Vietnam era generated abundant suspicion of military action. That suspicion only grew after the September 11, 2001, attacks, which generated particularly widespread and tenacious accusations of false flaggery. As Kathryn Olmsted notes in Real Enemies, September 11 conspiracy theorists “embraced” the concept that Operation Northwoods was a precursor to 9/11. Some of that was a matter of serendipitous timing: memos about Northwoods were declassified and put online in 1998, just in time for conspiracy-minded people to connect them to 9/11. Northwoods, Olmsted writes, served as “unassailable proof” for conspiracy theorists “that their theories of U.S. government-sponsored terrorism were horrifyingly plausible.”

9/11 truthers, as the suspicious are called, divide into two broad camps: those who believe the George W. Bush administration let the attacks happen on purpose and those who believe the administration made them happen on purpose (LIHOP and MIHOP, in shorthand). Both camps contain people who believe that the attacks created a reason for the administration to justify going to war and expanding its surveillance powers at home. The statistics on trutherism show that the numbers of believers were initially low, but they grew in the years following the attacks. This echoes the way the official story of the Kennedy assassination was increasingly questioned in the decades after, according to many polls, as the initial shock of the president’s murder faded and people began looking, as we often do, for deeper meaning.

With 9/11, the statistics on how conspiracy theorizing grew in the subsequent decade are readily available and very stark. As Jeremy Stahl wrote in Slate in 2011:

In May 2002, with Bush’s approval rating still well over 70 percent, fewer than one in 10 Americans in a CBS News poll said that the Bush administration was lying about what it knew regarding possible terror attacks prior to 9/11. By April 2004, 16 percent of respondents in a CBS News poll said that the Bush administration was “mostly lying” … while 56 percent said it was telling the truth but hiding something and 24 percent said it was telling the entire truth. By the five-year anniversary of the attacks, one in three Americans would tell pollsters that it was likely that the government either had a hand in the attacks of 9/11 or allowed them to happen in order to go to war in the Middle East.

Beyond their scope and persistence, the suspicions also generated one of the biggest conspiracy successes ever: the film Loose Change, made by independent filmmaker Dylan Avery, just twenty-one at the time; two decades later, hundreds of awful straight-to-Netflix conspiracy documentaries are still trying to replicate the phenomenon. Released in 2005, Loose Change argued that the 9/11 attacks were just the latest in a long string of false flags—Northwoods makes a pretty significant appearance in the film—and helped crystallize the theory that the Twin Towers were brought down by a controlled demolition. The attacks were, the film posited, an “inside job” meant to pave the way for a permanent, oil-grabbing war in the Middle East.

Both the impact of the film and the fact that “truther” beliefs continued to grow in the decade after 9/11 might be due to the same thing: some of the broader political points made by Loose Change are not actually all that far-fetched, for people on the right or the left. “In the aftermath of September 11, President Bush had and continues to have permission to do and say whatever he wants,” the narrator intones toward the end of the film. “All under the pretext of September 11. The Patriot Act. The Department of Homeland Security. Afghanistan. Iraq. It’s time for America to accept 9/11 for what it was: a lie which killed thousands of people, only in turn killing hundreds of thousands more, to make billions upon trillions of dollars.” After a multigenerational conflict in the Middle East more than fifteen years later, it’s hard to dispute that, at the very least, the attacks were politically beneficial.

In response to the success of Loose Change and other conspiracy-theorizing books and films about 9/11, the magazine Popular Mechanics devoted itself to debunking the scientific claims made by the conspiracy theories. Those include the idea that “jet fuel can’t melt steel beams,” by now such a well-known argument that it’s become a jokey shorthand for conspiracy thinking. The magazine eventually produced a book of its research. Not that it helped. Some level of 9/11 conspiracism remains common across the political spectrum. In 2016, the Chapman University Survey of American Fears found that more than half of those polled believed that the government is still hiding some of what it knows about the attack.

Mostly, though, theories about false flags or government responsibility stay firmly relegated to the fringe, confined among people who, for ideological reasons, very much want to find an alternate explanation for a violent event. The bombing of the Alfred P. Murrah Federal Building in Oklahoma City by Timothy McVeigh in 1995 is a case in point. The attack killed one hundred sixty-eight and wounded more than seven hundred; it was even more shocking because the Murrah Building housed a daycare center for the government workers’ children, and nineteen of them were among the dead.

The bombing posed a particular challenge to anti-government conspiracy theorists because it was carried out as retribution for what McVeigh saw as tyrannical government overreach: the deadly standoffs at Waco and Ruby Ridge. McVeigh intended the bombings to be the first spark in what he ultimately hoped would be a full-fledged revolution against the federal government. But the fact that civilians and children died in the attack made it not especially sympathetic, even for McVeigh’s fellow ideological travelers. After all, one of the horrors of the Ruby Ridge standoff was that it targeted a family, the Weavers, who sympathizers argued were only trying to live peacefully on a hilltop beyond the reach of a tyrannical Zionist government. During the standoff, the Weavers’ son Sammy, fourteen, his mother, Vicki, and their dog Striker were all shot and killed by FBI snipers.

It was, therefore, incumbent on people on the far right to come up with an alternate explanation for the Oklahoma City bombing. Alex Jones, the most famous and prolific spreader of false flag theories, got his start as an Oklahoma City truther, which he argued was not an attack by a lone, disgruntled domestic terrorist but a plot by a tyrannical government to consolidate power. According to a 2013 Esquire profile, Jones claimed that the bombing was part of a string of assaults on right-wing patriot groups and had been staged to justify a further crackdown on those groups.

Jones lost his job at an Austin public radio station after diving too deep into the false flag pool, leading him to found InfoWars and colonize what became an improbably large section of the media landscape. (In his book Them, Jon Ronson describes Jones’s early days broadcasting via an ISDN line out of one of his kids’ bedrooms, with “choo-choo train wallpaper and an Empire Strikes Back poster pinned on the wall.”) After 9/11, he had a lot more company: more and more events were labeled as false flags staged by the government by more and more people with blogs, YouTube channels, Twitter accounts, and websites. The targets of their investigations ranged from the mass shootings at Sandy Hook Elementary in Connecticut in 2012 and a San Bernardino community center in 2015, to the disappearance of Malaysia Airlines flight 370 in 2014 (which was speculated to have been carried out by the CIA or the Israeli government), and the 2017 suicide bombing at an Ariana Grande concert in Manchester, England (which some American conspiracy theorists thought was perpetrated to distract from the discussion around DNC staffer Seth Rich’s death). Interestingly, the first major school shooting, at Columbine High School, wasn’t a popular false flag theory when it took place in 1999, before the age of YouTube, easily buildable blogs, and widely used social media platforms. Instead, that shooting was retroactively identified as a possible false flag years later by the truther community.

On rare occasions, false flag theorizing can become so persuasive that it prompts real state action. Agenda 21, a conspiracy theory that rocketed to mainstream attention in 2012, was aided by then-prominent far-right TV star Glenn Beck. It held that the United Nations planned to invade the United States, seize everyone’s guns, and supplant the country’s sovereignty. (Agenda 21 was actually an entirely voluntary UN program for member countries that laid out various social improvements.)

Ted Cruz, then running for the U.S. Senate in Texas for the first time, appeared on Beck’s radio show to fret about Agenda 21, warning that it would result in the end of single-family homes, ranching, private cars, and, as he put it, “the American way of life.” That’s not a false flag; it’s just very, very stupid. (So stupid that the national Republican Party put an anti–Agenda 21 plank in its national platform: “We strongly reject the UN Agenda 21 as erosive of American sovereignty, and we oppose any form of UN Global Tax,” the declaration read.)

When Agenda 21 didn’t come to pass, its true believers decided that the UN planned to sneak it in the back door instead, disguising an armed invasion as something else entirely. In the summer of 2015, they identified their Trojan horse: Jade Helm 15, a massive military drill operation taking place across seven states.

The unabashed conspiracism that followed made its way to high levels of government. Texas governor Greg Abbott ordered the Texas State Guard to monitor Jade Helm, saying in a statement, “During the training operation, it is important that Texans know that their safety, constitutional rights, private property rights and civil liberties will not be infringed.” Abbott had echoed the fantastical line of the Oath Keepers, a far-right militia group that worried that Jade Helm was nothing less than a “portentous government plan”:

a pre-fabricated and preconstructed umbrella under which a black op by the Deep State’s compartmentalized agencies could possibly “Go Live” in a fantastic sort of Shock and Awe False Flag psycho-coup to jar the public mind of America through fear into acceptance of some nefarious policy the government desired, such as the establishment of Martial Law and the complete loss of individual liberty and our Constitution.

Jade Helm, then, was an exceptional example of a fake military exercise being twisted into a real one. It’s striking for the wide spread of the belief, particularly in Texas. A poll taken that summer by the University of Texas and the Texas Tribune showed that 39 percent of Texas voters supported Abbott’s plan to monitor the Jade Helm exercises. It also asked Texans about the probability of a military takeover: 44 percent thought the military would “likely be used to impose martial law,” while 43 percent thought it would be used to “confiscate firearms from citizens.”

Jade Helm was unusual, too, for its coherence. More or less everyone who believed in it seemed to agree that the invasion would be carried out in a particular fashion. That’s not usually the case with false flag theories. An event tends to generate a multitude of different suspicions, branches of a gnarled tree forking in hundreds of directions. Of the recent mass shootings, the murder of fifty-nine people with hundreds more wounded at the Las Vegas Harvest Music Festival generated a particularly high number and variety of conspiracy theories: it was orchestrated by an “Obama Administration intelligence contractor;” it was planned by the government, with the gunman brainwashed by psychiatric medication; it must have been a cover for something else.

The abundance of suspicion is partly due to the timeline of the shooting, which was deeply confused; the Las Vegas police revised it three times, and the order of events has never been entirely clear. One of the key witnesses, a security guard who was shot at by the gunman, went silent for five days and canceled several TV appearances. This of course fueled the conspiracy theories, though it seems likely he did so as a result of trauma rather than any suspicious motives. The gunman, Stephen Paddock, remained something of a mystery: his brother declared him “not an avid gun guy,” and his girlfriend swore she had no idea he was planning the attack.

It is no longer a surprise in this country when an aggrieved white man buys high-powered weapons and kills a lot of people, but for some reason the Las Vegas attack, because of these minor quirks, was broadly marked as “strange” or “suspicious” by a notable number of people on both the right and left. David French, a senior writer at the National Review and usually a fairly staid example of mainstream Republicanism, called the shooting “very, very strange,” “flat-out bizarre,” and “significantly different from virtually any other mass shooting in U.S. history,” though he declined to make clear what he was getting at.

One theory even suggested that this was a false flag attack planned by a foreign government, a semiotic twist we don’t usually see. Eric Garland, a self-described “futurist” and intelligence analyst who became infamous on Twitter during the 2016 elections for sprawling, apocalyptic threads, implied that the Las Vegas attack was somehow planned by Russian government sources. He claimed that Russia had prior knowledge of the attack, and that Russian trolls flooded the Internet with misinformation “minutes” after it took place. “Today’s reaction to Las Vegas was coordinated throughout the Deza-sphere,” he wrote, using the shorthand for dezinformatsiya (disinformation). “If you don’t know how this is working, get educated.”

Even a sitting Republican congressman got in on the action. Representative Scott Perry, a Republican from Pennsylvania, went on Fox News several months after the shootings to blame the whole thing on ISIS and Mexicans simultaneously. “I smell a rat, like a lot of Americans,” Perry told host Tucker Carlson. “Nothing’s adding up.” Nonetheless, he added, “Even more troubling than that, recently I’ve been made aware of what I believe to be credible evidence, credible information regarding potential terrorist infiltration through the southern border regarding this incident.” Perry never explained what the hell he meant, but he was following a classic, broad tactic in false flag conspiracizing: take a violent event that, on the surface, means one thing, and make it mean something entirely different—and much more politically valuable, given the climate against Mexican immigration.

Globally, false flag theories can have extremely sinister political uses. One particularly chilling international conspiracy theory claimed that the chemical attacks by the Syrian government against civilians were either staged or perpetrated by the White Helmets, a civilian aid and rescue group. That conspiracy theory built onto a broader skepticism of the attacks themselves: an investigation by the Guardian found that stories questioning how the attacks really happened began soon after Russia staged a military intervention in Syria in September 2015 to support the Assad regime, which was conducting airstrikes on opposition-held areas. “Almost immediately, Russian state media such as RT and Sputnik started falsely claiming that Isis was the only target,” reporter Olivia Solon wrote, as well as “throwing doubt” on whether “infrastructure and civilian sites” had been bombed.