Six and a half months before Adolf Hitler invaded Poland, New York City’s Madison Square Garden hosted a rally to celebrate the rise of Nazism in Germany. Inside, more than 20,000 attendees raised Nazi salutes toward a 30-foot-tall portrait of George Washington flanked by swastikas. Outside, police and some 100,000 protesters gathered.

The organization behind the February 20, 1939 event—advertised on the arena’s marquee as a “Pro American Rally”—was the German American Bund (“Bund” is German for “federation”). The anti-semitic organization held Nazi summer camps for youth and their families during the 1930s. The Bund’s youth members were present that night, as were the Ordnungsdienst, or OD, the group’s vigilante police force who dressed in the style of Hitler’s SS officers.

Banners at the rally had messages like “Stop Jewish Domination of Christian Americans” and “Wake Up America. Smash Jewish Communism.” When the Bund’s national leader, Fritz Kuhn, gave his closing speech, he referred to President Franklin Delano Roosevelt as “Rosenfield,” and Manhattan District Attorney Thomas Dewey as “Thomas Jewey.”

“We, with American ideals, demand that our government shall be returned to the American people who founded it,” declared Kuhn, a naturalized American who lost his citizenship during World War II. “If you ask what we are actively fighting for under our charter: First, a socially just, white, Gentile-ruled United States. Second, Gentile-controlled labor unions, free from Jewish Moscow-directed domination.”

Kuhn’s speech was interrupted by a Jewish-American man named Isadore Greenbaum who charged the stage in protest. Police and the vigilante force quickly tackled him, and proceeded to beat him up on stage. The crowd cheered as they threw him off stage, pulling his pants down in the process. Police charged Greenbaum with disorderly conduct and gave him a $25 fine, about $450 in 2019 dollars.

At the time the rally took place, Hitler was completing his sixth concentration camp; and protesters—many of them Jewish Americans—called attention to the fact that what was happening in Germany could happen in the U.S. “Don’t wait for the concentration camps—Act now!” proclaimed fliers advertising the protest. Outside the rally, people carried signs with messages like “Smash Anti-Semitism” and “Give me a gas mask, I can’t stand the smell of Nazis.”

In some cases, police responded to the protesters with violent attacks. In one instance, a protester escaped a mounted police officer who’d grabbed him by punching his horse in the face. As the rally broke up that night, some protesters were able to slip by police and punch departing Nazis in the face.