What led a young woman like Linda W. to join the army of IS? Some of the groups supporters seem to believe that in a world of holy warriors, joining the conflict as a heroic female fighter or becoming a wife and mother are key to continuing the spread of Islamic ideology from one generation to the next. Doesn't sound particularly appealing? It depends on how it's packaged.

Holy war and kittens

"There's a campaign tailored solely for women and young girls," explained Susanne Schröter, an ethnologist at the University of Frankfurt who studies Islamic society. While recruiting female members, terrorist organizations try to show their romantic side, she said.

IS members operate blogs featuring love stories that tell of girls and holy warriors traveling to the "caliphate."

"Especially successful are videos showing IS fighters holding kittens," said Schröter. The message: The IS fighter is not only brave and strong, but he's also a loving protector.

IS has has a tailored internet campaign to attract women to the militant group

"IS has a huge and impressive social media operation," said Schröter. It is "impressive," she added, because they not only operate on all the major social media channels, like Facebook, YouTube, Twitter and Instagram, but they also tailor their messages to target specific groups.

The 16-year-old German schoolgirl Linda W., who came from the town of Pulsnitz in the eastern state of Saxony, corresponds precisely to the type of person IS seeks to recruit using this cutesy, romantic social media content. "It's a contrast to the gruesome videos they use to recruit young men," explained Schröter.

Luring via the internet

Questions about life and religion can lead young people to join IS as well. "It can ... begin with a simple interest in Islam, with someone hoping to find answers to the meaning of life," said sociologist Stephan Humer, who studies terrorism and extremism on the internet.

In the early days of IS, when the terrorist organization's presence on the internet was still largely unexplored, Humer and his colleagues found that a search for terms like "jihad" or "Sharia" quickly led to sites with links to the group. "Here the random search is the intention," said Humer, adding that in this way, IS was able to intercept interested parties early on and feed them propaganda.

"Those who wanted to know more were then led to forums where they met people for the first time," he said.

Community, support, family

"It's classic psychology," explained Humer: Whether in the supermarket, the mosque or an online forum, someone who's stopped and asked if he wants something is more likely to buy what is offered to him.

"What IS offers is community and support, which young people especially crave," Humer said. The promise is: Come with us, our community has everything you could wish for.

The young people that fall for this promise are soon on their way to the war zones of the self-proclaimed "caliphate." And unfortunately, said the ethnologist Schröter, "it's difficult to reach young people in the radicalization process."