Before the gunman shot down 10 Black people in Buffalo, New York, at a supermarket on Saturday afternoon, he had stated his intent: “kill as many Black people as possible.” He reportedly wrote these words in a 180-page screed published online before he carried out what investigators are calling a hate crime and a racist act of violent extremism.

The 18-year-old white man, who claimed to drive hours to the zip code he targeted in Buffalo because it “has the highest black percentage that is close enough to where I live,” repeatedly lamented immigration, which he feared would result in “ethnic replacement,” “cultural replacement,” “racial replacement,” and ultimately, he wrote, “white genocide.”

This is the “white replacement theory” or the “Great Replacement” that has motivated similar mass killings in recent years — the racist conspiracy theory that holds that, through immigration, interracial marriage, integration, and violence, and at the behest of secret forces orchestrated by “global elites” (as the Buffalo shooter claimed) or Jews, white people are being disenfranchised, disempowered, and pushed out of “white nations.”

These ideas are not new. They have been documented for at least a century, the forces of white fear that shaped the national origin quotas of the 1920s. They have inspired mass attacks — and also smaller-scale instances of violence — that have claimed the lives of hundreds of people in the United States and abroad.

A brief history of the flawed — and racist — replacement conspiracy theory

In the United States, white people’s fear about being replaced by “outsiders” and migrants of “inferior” backgrounds has a long history. These fears were especially apparent in the early 1900s when white intellectuals openly explored and shared ideas about displacement that shaped immigration policies and other laws.

A leading proponent was Madison Grant, a lawyer, eugenicist, and conservationist who published The Passing of the Great Race in 1916, arguing that the supposedly superior “Nordic” race was in danger of extinction in the United States. Grant advocated for sterilization programs for supposedly inferior races, immigration restrictions, and anti-miscegenation laws that would stop any intermingling between racial groups.

Grant’s work had lasting consequences, influencing the lawmakers who drafted the Immigration Act of 1924, which limited the number of immigrants from southern and western Europe for 40 years. His work left an impression on President Theodore Roosevelt, who praised it as “a capital book”; President Calvin Coolidge echoed Grant’s ideas in a 1921 Good Housekeeping article, “Whose Country Is This?” claiming that the US should reject being regarded as a “dumping ground” for an “advancing horde of aliens.” Adolf Hitler, meanwhile, referred to Grant’s work as his bible.

Grant was not alone in making his argument. Four years later, an adherent of his, historian Lothrop Stoddard, published The Rising Tide of Color: The Threat Against White World-Supremacy, in which he similarly warned that the Nordic race would be eliminated or absorbed by “alien hordes” of immigrants that he viewed to be of lesser value including “Alpines, Mediterraneans, Levantines and Jews.” He called for race solidarity among white people to preserve what he considered “good stocks.” Stoddard, too, influenced elected officials like Warren G. Harding, who praised the book in a public speech in 1921, and leaders abroad in Britain, Australia, Canada, New Zealand, and Nazi Germany.

By the end of World War II, the ideas that Grant and Stoddard promulgated were largely disavowed by elites for their association with the Nazis and the Holocaust. But they didn’t disappear. US senator and former governor of Mississippi Theodore G. Bilbo published the book Take Your Choice: Separation or Mongrelization in 1947, in which he argued that the “Caucasian race,” which he credited with creating civilization, was “in jeopardy” from Black people, whom he considered “mongrels” who could not “maintain a culture.”

The 1970s saw the use of the phrase “white genocide” in the official newspaper of the National Socialist White People’s Party (formerly the American Nazi Party), which argued “birth control campaigns” would make whites “outnumbered four to one.” Jean Raspail’s 1973 dystopian fantasy novel Camp of the Saints, depicted a world in which France and the Western world is invaded by foreign dark-skinned refugees — a text “widely revered” by white supremacists, according to the Southern Poverty Law Center.

The controversial 1994 book The Bell Curve argued that the United States was encouraging the “wrong women” to have babies, and that “the intelligence of immigrants is a legitimate topic for policymakers to think about” since “Latin and black immigrants are, at least in the short run, putting some downward pressure on the distribution of intelligence.”

French philosopher and white nationalist Renaud Camus helped give the theory new life in a 2012 book, Le Grand Remplacement. In a 2017 interview with Vox following the Charlottesville “Unite the Right” rally, Camus argued that the extremists who chanted “we will not be replaced” had reason to be concerned that the United States could change into “just another poor, derelict, hyperviolent, and stupefied quarter of the ‘global village.’”

At the core of replacement theory is the concept of protecting a white “race” — one that is not necessarily bound by borders but simply held together by racist ideas of white power and supposed white dominance.

Replacement theory is the link connecting racist violence

The Turner Diaries, a 1978 novel about a race war that eliminates all nonwhites, directly inspired the Oklahoma City bomber, who killed 168 people. The same text inspired the Norwegian far-right extremist who killed 77 people, mostly immigrants, in a bombing and gun rampage in 2011, saying he was fighting “mass immigration.”

The Norway extremist inspired the New Zealand shooter, who killed at least 50 Muslim worshippers at mosques in Christchurch, New Zealand, in 2019, leaving behind a document that explained an alleged “assault on European people.”

And the New Zealand shooter particularly inspired the Buffalo shooter, according to his 180-page screed.

Kent Nishimura/Los Angeles Times/Getty Images

Replacement theory forms the strands that connect this web of violence — from the Oklahoma bomber to Norway to New Zealand to Buffalo. As University of Chicago historian Kathleen Belew told Vox following the Christchurch massacre in 2019, white supremacists motivated by replacement theory and white power see themselves as fighting for “the Aryan nation.”

The connections don’t stop there. The shooter who killed 23 people in El Paso, Texas, in 2019 claimed he acted in response to “the Hispanic invasion” of the state.

In 2018, a man who blamed Jewish people for helping to resettle immigrants killed 11 Jewish people at the Tree of Life synagogue in Pittsburgh.

The white man who killed nine Black churchgoers in Charleston, South Carolina, in 2015 claimed to be concerned about “living in the melting pot”; the white man who stabbed two people to death on a train in Oregon in May 2017, after harassing two Muslim women, adhered to the idea that there should be a “white homeland for whites only.” The man who opened fire in a California synagogue, killing one and injuring three others in 2019, wrote in an open letter that Jews were preparing a “meticulously planned genocide of the European race” and cited the Christchurch and Pittsburgh shootings as inspiration.

The white people who gathered in Charlottesville, Virginia, in 2017 for the Unite the Right rally, where a white supremacist struck and killed a woman with his car, chanted “you will not replace us” and “Jews will not replace us.”

Replacement theory has become mainstream among Republicans

Meanwhile, the rhetoric of replacement theory has become increasingly prominent among some Republicans. Party members have espoused tenets of replacement theory, and some have supported it by name, to help bolster anti-immigration sentiments and policies.

Throughout his presidency, Donald Trump repeatedly employed the arguments and tropes that form the basis of replacement theory — that white people were facing “white genocide” as a result of an “invasion” from foreigners. “We don’t want what is happening with immigration in Europe to happen with us!” Trump tweeted in 2018. The former president’s latest presidential campaign posted more than 2,000 ads that featured the word “invasion,” according to a New York Times analysis.

Following Trump’s fearmongering that a migrant caravan of Central Americans was on its way to the US’s southern border, other lawmakers adopted the language. Rep. Paul Gosar (R-AZ) has repeatedly tweeted about an invasion that lawmakers need to take action against.

Former Iowa Rep. Steve King, who was in Congress from 2003 to 2021, constantly voiced fears about replacement. In 2017 he tweeted, “We can’t restore our civilization with someone else’s babies,” once retweeted a Nazi sympathizer’s fears about migration, and celebrated Hungary’s authoritarian leader Viktor Orbán for denouncing “mixing cultures.”

Fox News’ Tucker Carlson has perhaps become the foremost champion of replacement theory on the right. In about 400 episodes of his show since 2016, according to a New York Times analysis, he shared ideas about replacement. He even used the idea to defend the people who carried out the January 6, 2021 insurrection at the US Capitol. “In political terms, this policy is called the great replacement, the replacement of legacy Americans with more obedient people from faraway countries,” Carlson said on his program last year in response to the Haitian migrants who arrived at the border.

Rep. Matt Gaetz (R-FL) defended Carlson’s interpretation of replacement theory on Twitter, saying the news host was “correct” in his analysis of “what is happening to America.”

There’s some evidence that these ideas are resonating with Americans. A large poll conducted by the Associated Press and NORC in late 2021 found that about one in three US adults thinks that there is a plot underway to replace US-born Americans with immigrants. Republicans were more likely than Democrats to believe that native-born Americans are losing economic, political, and cultural influence because of immigration.

Replacement theory has a long history, but no longer lies dormant — if it ever did — in the past, or in the black holes of the internet. The conspiracy allows white supremacist violence to remain “the most persistent and lethal threat” in America, as long as the country fails to root it out.