In 1935, Nazi Germany passed two radically discriminatory pieces of legislation inspired by American laws: the Reich Citizenship Law and the Law for the Protection of German Blood and German Honor. Together, these were known as the Nuremberg Laws, and they laid the legal groundwork for the persecution of Jewish people during the Holocaust and World War II.

When the Nazis set out to legally disenfranchise and discriminate against Jewish citizens, they weren’t just coming up with ideas out of thin air. They closely studied the laws of another country. According to James Q. Whitman, author of Hitler’s American Model, that country was the United States.

“America in the early 20th century was the leading racist jurisdiction in the world,” says Whitman, who is a professor at Yale Law School. “Nazi lawyers, as a result, were interested in, looked very closely at, [and] were ultimately influenced by American race law.”

In particular, Nazis admired the Jim Crow-era laws that discriminated against Black Americans and segregated them from white Americans, and they debated whether to introduce similar segregation in Germany.

Yet they ultimately decided that it wouldn’t go far enough.

“One of the most striking Nazi views was that Jim Crow was a suitable racist program in the United States because American Blacks were already oppressed and poor,” he says. “But then in Germany, by contrast, where the Jews (as the Nazis imagined it) were rich and powerful, it was necessary to take more severe measures.”

Because of this, Nazis were more interested in how the U.S. had designated Native Americans, Filipinos and other groups as non-citizens even though they lived in the U.S. or its territories. These models influenced the citizenship portion of the Nuremberg Laws, which stripped Jewish Germans of their citizenship and classified them as “nationals.”

But a component of the Jim Crow era that Nazis did think they could translate into Germany were anti-miscegenation laws, which prohibited interracial marriages in 30 of 48 states.

“America had, by a wide margin, the harshest law of this kind,” Whitman says. “In particular, some of the state laws threatened severe criminal punishment for interracial marriage. That was something radical Nazis were very eager to do in Germany as well.”

The idea of banning Jewish and Aryan marriages presented the Nazis with a dilemma: How would they tell who was Jewish and who was not? After all, race and ethnic categories are socially constructed, and interracial relationships produce offspring who don’t fall neatly into one box.

Again, the Nazis looked to America.

“Connected with these anti-miscegenation laws was a great deal of American jurisprudence on how to classify who belonged to which race,” he says.

Controversial “one-drop” rules stipulated that anyone with any Black ancestry was legally Black and could not marry a white person. Laws also defined what made a person Asian or Native American, in order to prevent these groups from marrying whites (notably, Virginia had a “Pocahontas Exception” for prominent white families who claimed to be descended from Pocahontas).

The Nuremberg Laws, too, came up with a system of determining who belonged to what group, allowing the Nazis to criminalize marriage and sex between Jewish and Aryan people. Rather than adopting a “one-drop rule,” the Nazis decreed that a Jewish person was anyone who had three or more Jewish grandparents.

Which means, as Whitman notes, “that American racial classification law was much harsher than anything the Nazis themselves were willing to introduce in Germany.”

It should come as no surprise then, that the Nazis weren’t uniformly condemned in the U.S. before the country entered the war. In the early 1930s, American eugenicists welcomed Nazi ideas about racial purity and republished their propaganda. American aviator Charles Lindbergh accepted a swastika medal from the Nazi Party in 1938.

Once the United States entered the war, it took a decidedly anti-Nazi stance. But Black American troops noticed the similarities between the two countries, and confronted them head-on with a “Double V Campaign.” Its goal? Victory abroad against the Axis powers—and victory at home against Jim Crow.