This Friday marked Holocaust Remembrance Day, the 72^nd anniversary of the Soviet liberation of Auschwitz-Birkenau—a network of Nazi concentration and extermination camps that claimed the lives of an estimated 1.5 million people, most of them Jews. President Donald Trump chose to commemorate the occasion by releasing a public statement omitting any mention of Jews or the scourge of anti-Semitism (breaking with past GOP and Democratic tradition), and signing an executive order barring refugees and citizens of seven Muslim-majority countries from entering the United States, including Syria, Iraq, Iran, Libya, Somalia, Yemen, and Sudan.

“It’s repulsive,” Mark Hetfield, president and CEO of the Hebrew Immigrant Aid Society, told CNN. “I mean, the timing is incredibly offensive. It was during the Holocaust that the world shamefully refused to give asylum to Jews and to others who were being murdered or about to be murdered in Nazi Germany.”

Indeed, during the Holocaust, as millions of Jews were being slaughtered by the Nazis, the United States enforced strict immigration quotas against Jews from Germany and Eastern Europe.

In June 1939, the ocean liner St. Louis sailed into the Port of Miami with 937 refugees onboard—nearly all Jewish and seeking asylum in the United States. They’d already been turned away from Cuba and Canada, and when they were denied entry into America, the ship was forced to return to Europe where many of its passengers were killed in the Holocaust. Even Anne Frank’s family made several desperate attempts to emigrate from Europe to America, only to be denied visas.

This closed-door policy was an extension of the Immigration Act of 1924, which sought to, in the words of dissenting Jewish-American politician Emmanuel Celler, create “a distinct American identity by favoring native-born Americans over Southern and Eastern Europeans in order to ‘maintain the racial preponderance of the basic strain on our people and thereby to stabilize the ethnic composition of the population.’” Both Congress and the public believed that these Southern and Eastern European immigrants, many of whom were Jewish, would take away jobs from Americans plagued by the Depression, and were racially inferior. Asians and Arabs were banned entirely.

There was also widespread paranoia concerning a “fifth column,” or the theory that, should Germany or Japan invade the U.S., embedded spies from those countries would help destroy America from the inside. This led to the cruel internment of Japanese-Americans, and the curbing of U.S. visas to those from Axis countries.

At a June 5, 1940, press conference, President Franklin D. Roosevelt stated: “Now, of course, the refugee has got to be checked because, unfortunately, among the refugees there are some spies, as has been found in other countries. And not all of them are voluntary spies—it is rather a horrible story but in some of the other countries that refugees out of Germany have gone to, especially Jewish refugees, they found a number of definitely proven spies.”

This fear of immigrant spies was mostly just that. With the exception of a few highly publicized cases, including that of 28-year-old German Herbert Karl Friedrich Bahr, there’s been no evidence of a mass influx of immigrant spies during this time. In fact, there exist striking parallels to the GOP and President Trump’s Muslim immigrant panic of today, given that, of the 784,000 refugees settled in America between September 11, 2001, and October 2015, only three have been arrested for plotting terrorist acts. “And it is worth noting two were not planning an attack in the United States and the plans of the third were barely credible,” wrote Kathleen Newland of the Migration Policy Institute. The terrorists behind the San Bernardino shooting, Pulse nightclub massacre, and Boston Marathon bombing were all U.S. citizens.

Earlier this month, the film German Concentration Camps Factual Survey was quietly released into select North American theaters. Produced by Sidney Bernstein, advisor to the British Ministry of Information, and co-directed by his pal Alfred Hitchcock, the documentary is comprised of footage shot by Allied American, British, Soviet, and Canadian combat cameramen as they liberated ten concentration camps, including Auschwitz, Bergen-Belsen, Buchenwald, Dachau, and Majdanek. The images are unforgettable, from Nazi physician Fritz Klein being interviewed on top of a pile of bodies at Bergen-Belsen to long, uninterrupted pans capturing stacks of eyeglasses, wedding rings, toothbrushes, human teeth, and bags of hair collected by the Nazis. There are even collections of lampshades made of human skin.

“The panning shots were Hitchcock’s idea,” says Jane Wells, the daughter of Bernstein whose non-profit, 3generations, put out Factual Survey. Hitchcock advised Bernstein and his crew of soldier-documentarians by phone, and suggested the continuous takes because “he felt that people wouldn’t believe what they were seeing otherwise.”

Unfortunately, the film was never completed for a variety of reasons. It wasn’t until 2008 that the Imperial War Museum, using the original filmmakers’ rough cut, script, and shot list, finalized the editing process. The 75-minute finished film premiered 69 years after it was shot, at the 2014 Berlin International Film Festival.

“I tried to enumerate the different explanations,” Wells tells me, before taking out a notepad and reading from it. “One was the fear it would alienate Germans when they were trying to rebuild Germany after the war. The second one is the British government didn’t want to build support for a Zionist state. The third is they didn’t want to create undue sympathy for Jews in particular, or to single Jews out for poor treatment. And the fourth one, which is the Imperial War Museum’s theory, is that its time had come and it had missed its moment.”

Its shelving was devastating to Bernstein, who refused to speak publicly about what Wells calls his “great secret” until he was interviewed for the 1985 documentary A Painful Reminder, which contained footage from his film. Parts of Factual Survey were also used in Billy Wilder’s 22-minute concentration camp documentary Death Mills (Die Todesmühlen), released in January 1946.

“Unless the world learns the lesson these pictures teach, night will fall,” Factual Survey’s narrator says. And according to Wells, “it’s hard not to see the parallel to today,” given the rise of white nationalism in the U.S. and abroad corresponding with the rise of Trump, candidate Trump dog-whistling to white nationalists during his campaign by sharing anti-Semitic memes that originated on neo-Nazi online message boards, and the ascendance of Steve Bannon, former overlord of the “alt-right” publication Breitbart turned Trump right-hand man, who’s been accused of serial anti-Semitism.

“To me, it’s horrific. I’d love to invite the President and Jared Kushner to come see this film, and love to encourage any Jews who supported Trump to come see this film. I know Jews who voted for Trump, and if you ask them about the rise of white nationalism or the ‘alt-right’ in the wake of Trump, they’ll say, ‘Oh, well his son-in-law is a Jew! His daughter keeps a kosher kitchen, how bad can it be?’” say Wells. “The rise of the ‘alt-right’ is completely awful. The way Jews have been called out on Twitter is horrible and disgraceful. I’d like some of these ‘alt-right’ people to also come see this film and try and explain to me why they think this didn’t happen or didn’t matter.”

“If you see this footage, “ she adds, “there is no way on God’s earth that you can argue this didn’t happen.”

Wells had initially planned to release German Concentration Camps Factual Survey theatrically on Jan. 27, 2015, in honor of the 70^th anniversary of the liberation of Auschwitz. The film didn’t make it to cinemas until January 6^thof this year, but she believes that, given the Syrian refugee crisis, it “will have more of an impact today than it would have even then.”

“It is a cry for reconnecting to our humanity, and I think that is a message that is very resonant today,” offers Wells. “When I look at the atrocities that are happening in Syria today, when I look at the situation with Native Americans in North Dakota, when I look at the rise of the fascistic far-right globally, it seems like we have forgotten some of our common humanity.”

Today, Jan. 27, marks the 72nd anniversary of the liberation of Auschwitz. That event did not mark the end of the Holocaust—gassings continued until the eve of Hitler’s suicide on April 30, 1945, and thousands more died of the effects of starvation and mistreatment at places like Belsen even weeks after their liberation.

But Jan. 27 should put us in mind of the beginnings. How did this happen? In particular, how could Germany, by all outward indications a civilized and modern country, become a persecuting society, brutally indifferent to the fates of anyone outside its supposed “people’s community”?

These questions should worry people for all time.

Adolf Hitler was a minority choice to lead his country; when he took office, roughly 55 percent of Germans had never voted for him. Anti-semitism was prevalent in German culture but by no means dominant or respectable. The nation’s elites (the establishment) generally regarded the Nazi führer with disdain and mistrust and doubted his capacity to run a government, given his complete lack of experience at doing so. The consensus about the Nazis’ wild-eyed promises was captured by the oft-repeated German proverb, “Nothing is eaten as hot as it’s cooked.”

Six years later, most Germans were acquiescing, and many of them were trying to benefit from, the complete humiliation and dispossession of German Jews, their demotion to “subjects” of the Reich, and their forced expulsion from the country. Three more years on, most Germans, including those elite corporate leaders and civil servants who scorned Hitler in 1933, were not just turning a blind eye to, but facilitating enslavement and mass murder… and finding a great many helpers in the Axis-occupied and Axis-allied regions of Europe.

The key to understanding the transformation of Germans’ behavior is straightforward: power magnifies the ideas of those who hold it. Power enabled the Nazi regime to unleash the haters, to intimidate the squeamish, and to change the moral valence of prejudice from something frowned upon to something glorified as patriotic. Once that happened, individual self-interest took care of the rest.

Above all, power enabled the propagandists for Nazism to divide the world relentlessly into Us vs. Them and to shut down more nuanced perspectives. To Germans, the world became a perpetual struggle between poor, virtuous, and victimized Us, and malevolent, conspiratorial, and implacable Them. In such an unforgiving environment, all means of self-defense were justified, including preemptively striking Them—taking their rights away, concentrating them in camps and ghettos, wiping them out—before they supposedly had a chance to do their worst.

Demonization of “Them” is always the first step toward persecution and genocide. And an essential prerequisite for demonization is its proponents’ sense of victimization, of having been or being about to be robbed of a birthright. The adherents of modern anti-semitism, not only in Germany but elsewhere in Europe, were people displaced and diminished by the Industrial Revolution and threatened by the specter of communism. In our own day, the devotees of nativist populism, not only in the U.S. but also in Europe, are people declassed and disoriented by the digital revolution and alarmed by the rise of Islamism. Will they go the way of the Nazis toward ever escalating paranoia and persecution?

Only if governments help them. Populist movements, on their own, can’t make persecuting societies or generate genocides. These phenomena need office-holders to countenance, stimulate, and implement hatred. Only when powerful leaders choose to let discrimination and violence take hold, and then to accelerate these lusts, does systematic degradation, let alone mass murder, result.

That is the challenge the Holocaust poses all these years later: Which way will political leaders go? Toward feeding angry and vengeful segments of public opinion or toward promoting pluralism and progress? Because the prospects look chancy right now, we should all recall the words of another German proverb—“Beware the Beginnings”—and be ready to act on it.

Peter Hayes is professor of history and German and Theodore Zev Weiss Holocaust Educational Foundation professor of Holocaust studies emeritus at Northwestern University. W. W. Norton & Co. published his new book,Why? Explaining the Holocaust, on Jan. 17.