Sara J. Bloomfield is the director of the U.S. Holocaust Memorial Museum.

A man carrying a Nazi flag in Charlottesville this month. (Steve Helber/AP)

In an era when emoji, memes and logos can drive a national conversation, symbols are more powerful than ever. Americans are grappling with the tragic loss of life and eruption of neo-Nazism in Charlottesville this month. What does it say about our society that neo-Nazi and white-supremacist symbols and slogans were deployed in the streets of 21st-century America? What is striking is how much of what was on display was taken directly from Nazi Germany and Holocaust-era fascist parties.

Longtime Holocaust denier and Ku Klux Klan member David Duke, Matthew Heimbach and their like-minded followers who brought those symbols into public view that day know their resonance and use them deliberately. Many of these words and images were once hidden away in dark corners of the Internet, a coded language spoken by white-nationalist believers. Now they are being brought into the open, and it is incumbent upon all Americans to understand their origins, what they represent and the dangers they pose.

The swastika is the most recognizable symbol of Nazi propaganda. Despite its ancient history, by the early 20th century it was adopted by a number of far-right nationalist movements and became associated with the idea of a racially “pure” state. Adolf Hitler personally designed the Nazi flag with a black swastika positioned at the center of a white disk on a red background.

However, other lesser-known Nazi references were evident throughout the rally, including chants of “blood and soil.” The concept of “Blood and Soil” (in German, “Blut und Boden”) was foundational to Nazi ideology. “Blood” referred to the goal of a “racially pure” Aryan people. “Soil” invoked a vision of territorial expansion and was used to justify land seizures in Eastern Europe and the forced expulsion of local populations in favor of ethnic Germans. The term was a rallying cry during the 1920s and early ’30s, when the Nazis and other far-right political parties opposed the fledgling Weimar German democracy. This concept played on resentment about German territories lost under the terms of the post-World War I Treaty of Versailles.

Last week in Charlottesville, Heimbach wore a T-shirt emblazoned with the image of Corneliu Zelea Codreanu. While few Americans could identify him, white nationalists know him as a violent anti-Semite and the leader of the main Romanian fascist organization formed in the 1920s, the Legion of the Archangel Michael, also known as the Iron Guard. Codreanu was killed in 1938, but his ideology continued to animate Romanian fascism. The Romanians were directly responsible for the second-largest number of Holocaust victims after the Germans.

Duke and Heimbach and their ilk are not Hitler, but they are inspired by the same worldview — that history is ultimately a racial struggle and that pluralism and the dignity of all individuals, ideals that most Americans espouse, are weaknesses that must be overcome if the “Aryan race” is to survive.

The Nazis eventually launched a world war and imposed this racial worldview across occupied Europe. Six million Jews and millions of others were murdered and persecuted because they were deemed “inferior.” The Holocaust teaches us the dangers of unchecked hatred and that while it may start with the targeting of one group, it always spreads.

Elie Wiesel, the U.S. Holocaust Memorial Museum’s founding chairman, envisioned it as a living memorial to the victims of the Holocaust, serving as a cautionary tale and an urgent message — about human nature, our capacity for evil and the fragility of societies.

History speaks to us for a reason. But we can only heed its warning if we are listening.

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