Written by Cynthia Miller-Idriss Contributors Muhammad Darwish, Max Fraser, Anita Gill, Ed Kiernan, Alex Sears, Ignacio Osorio

Cynthia Miller-Idriss is a professor of education and sociology at the American University in Washington, DC. She is the author of "The Extreme Gone Mainstream" (Princeton University Press), which explores how extremism is going mainstream in Germany through clothing brands laced with racist and nationalist symbols.

The enduring image of the racist skinhead, with his signature shaved head, black combat boots and bomber jacket, has all but disappeared.

In its place is a fragmented set of mainstream styles and streetwear brands that use coded symbols and messages to market extremist politics, turning T-shirts and hoodies into walking billboards to communicate with insiders and outsiders alike. Especially popular across Eastern Europe and Russia, the clothing is often high-quality, with T-shirts alone costing upwards of $35.

In my interviews with 51 youth in and around far-right scenes in Germany (all of whom were apprentices in construction trades), I found that this clothing is far from just a reflection of youth identity. It also helps mobilize the far-right.

One way this happens is by opening access to certain far-right environments. One 16-year-old self-identified right-wing nationalist told me that clothing can act as a ticket to underground concerts and events where youth aren't already known. The coded messages of their dress send signals to insiders.

A member of the National Radical Camp (ONR) demonstrates against immigration in Warsaw, Poland wearing a hoodie from the brand Red is Bad. Credit: NurPhoto via Getty Images

Sometimes, alphanumeric sequences of numbers and letters stand in for racist or nationalist phrases. ("2YT4U," for example, means "too white for you.") Other coding deliberately plays on what's called the "gray zone," offering plausible deniability to law enforcement, teachers, parents and other authorities. Thus, a purple T-shirt that says, in big white block letters, "MY FAVORITE COLOR IS WHITE," could be read as a white supremacist message or as a humorous play on the color of the shirt.

In more overt examples, the clothing spreads nationalist and extremist ideals with symbols, iconography and messages that call on consumers to be patriotic, celebrating the nation, country and whiteness. References to myths and historical events, like the Crusades or Reconquista (a Spanish pogrom against Muslims in the Middle Ages), are sometimes paired with mentions of contemporary regional tensions, so that the phrase "Reconquista Crimea" hints at a violent expulsion of Muslims from Crimea.

An attendee at a Warsaw march marking the 100th anniversary of Poland regaining independence waves a U.S. Confederate flag. Credit: NurPhoto via Getty Images

Much of the nationalist messaging also connects to the global far right. A Polish nationalist streetwear brand sells a T-shirt depicting the US Confederate flag. Other Eastern European and Russian brands widely adopt runic and Viking symbols, which appeal to German far-right groups who believe Germanic tribes descended from Nordic tribes whose origins were Aryan. References to Nazi history are common internationally, and English text -- in phrases like "White Fist," "Hate Club," "Rising Storm," "Zero Tolerance" and "Warrior" -- is ubiquitous.

Finally, the clothing helps mobilize extremism with emotional appeals that facilitate a sense of belonging with like-minded others who, as one young man told me, "can't exactly identify with mainstream society."

Constant references to ideals like brotherhood, belonging, loyalty, glory, creed, nation and race help foster a sense of belonging, while singling out those who don't belong. These messages are paired with calls for revolution and resistance, and images of skulls and weapons like brass knuckles, axes, knives and guns. In this way, the clothing literally embodies violence and combat.

The German Thor Steinar brand is often associated with the neo-Nazi movement. Credit: picture alliance via Getty Image

Nationalist streetwear is not the sole driver of radicalization, of course. But along with far-right music lyrics, internet forums, YouTube videos and political rhetoric from far-right leaders, clothing can intensify exposure to ideological claims. These brands encourage consumers to accept an ideology that positions us against them in a war to the end, valorizes violence as the moral solution and calls on individuals to join the righteous fight to restore the nation or white heritage.

They use iconography and messaging that dehumanizes migrants and minorities, legitimizes and celebrates violent revolution, identifies the "evil other" and calls on the righteous to take action.

In this sense, nationalist streetwear acts as a gateway to extremism. It socializes youth toward extremist values and ideals while offering a noble quest and sense of purpose and identity, all the while softening racist and xenophobic expression through humor and clever, coded references.

T-shirts are more than just T-shirts, in other words. As part of a broader youth subculture, they can strengthen racist and nationalist identification and mobilize extremist action and violence.