The violence that took place this Shabbat morning at the Tree of Life congregation in Pittsburgh is the fear of every synagogue, Hillel, day school, and Jewish community center in this country. It is the ancient Jewish expectation of persecution—when, where, has it not been with us?—married to American reality: a country saturated with guns and habituated to quotidian massacre, plagued by age-old racism and bigotry, which have lately been expertly inflamed by the holder of the highest office in the land.

For the past few years, American Jews have glanced warily at Western Europe, where anti-Semitism, never dormant, is once again on the rise. The British Labour Party has been riven by accusations of anti-Semitism among its leadership. French Jews have emigrated to Israel in unprecedented numbers. In Sweden, synagogues and Jewish centers have been firebombed. After 9/11, American synagogues and community centers became barricaded spaces, outfitted with concrete sidewalk barriers and metal detectors, so that going to services felt like going to the airport. The concern then was an external threat.

There has long been a casual assumption that homegrown anti-Semitism could not happen here, that “The Plot Against America” would remain the fantastical counter-factual that Philip Roth intended it to be. And yet, the warning signs have become increasingly clear. Since the 2016 Presidential campaign, anti-Semitic vitriol has exploded on the Internet. Neo-Nazis tweet swastikas and Hitler-era propaganda of leering, hook-nosed rabbis. Holocaust deniers discuss “The Protocols of the Elders of Zion” in plain view. Jewish journalists and other public figures have had their profile pictures Photoshopped onto images of lampshades and bars of soap. The name “George Soros” is no longer invoked as a dog whistle, but as an ambulance siren. “The Jewish question” is debated on alt-right blogs and news sites. In the run-up to the election, anti-Semites began to put Jewish names in sets of triple parentheses—a yellow star for the digital age, by which to un-assimilate the assimilated. Jews rushed to claim and defang the symbol, turning it into a voluntary declaration of pride, but the scar of its origins remains. For a time after Donald Trump’s election, I collected screenshots of racist and anti-Semitic hate speech I came across. Then I stopped. The proof was everywhere, plain as day.

It seems clear that anti-Semitism has burrowed into the American mainstream in a way not seen since the late nineteen-thirties and early nineteen-forties, when it also fused easily with conservative isolationist fervor and racism. In “These Truths,” her masterful new history of this country, my colleague Jill Lepore writes about the anti-Semites of that period, who saw “mass democracy and mass culture as harbingers of the decline of Western civilization.” In 1939, the German-American Bund held a pro-Nazi rally at Madison Square Garden, attended by twenty thousand people; you can watch footage of it here, and, as vile as it is, I suggest that you do. Amid the sieg-heils, you will see Fritz Kuhn, the Bund’s leader, railing against the “Jewish-controlled press” as he lays out his vision for a “socially just, white, Gentile-ruled United States.” “We, with our American ideals, demand that the American government shall be returned to the American people who founded it,” he says, to cheers.

Not long ago, I came across a description—published in the March, 1939, bulletin of the men’s club at New York’s Ansche Chesed synagogue—of a counter-rally held a couple of weeks later, at Carnegie Hall. “Stressing that racial intolerance was un-American, speaker after speaker denounced the activities of the German-American Bund,” the bulletin reports. “The need for protecting our democratic processes was on the lips of everyone and strong sentiment of solidarity to protect democracy and racial and religious freedom that goes with it was prevalent throughout.” That sense of solidarity, which, for me, as for many, is at the moral center of the American-Jewish experience, was explicitly attacked in Pittsburgh on Saturday. It has been reported that, a few weeks ago, the alleged gunman furiously railed on social media against HIAS, the Hebrew Immigrant Aid Society, which was founded, at the turn of the last century, to help the waves of Jewish immigrants who left imperial Russia for America. The organization later worked to resettle Jews fleeing Nazi Germany, and currently serves immigrants and refugees of all backgrounds. It is a bitter irony that that sense of common cause has now been further strengthened, as the Tree of Life joins Mother Emanuel A.M.E. Church, in Charleston, South Carolina, Dar Al-Farooq Islamic Center, in Bloomington, Minnesota, and so many other houses of worship as points on a dark map of ongoing American tragedy.