Ali began noticing them in the early fall, the men on street corners of his heavily Muslim neighborhood who hoped to "talk about Islam" with him.
"It was clear what they really wanted," he said — for him to fight for Islamic State in the Middle East. "And I watched as friends — people I went to school with, regular people — listened and did whatever they said after just a few weeks, like … [buying] a new pair of shoes."
As he smoked a cigarette outside a cafe in Berlin's Neukoelln neighborhood, Ali, 22, offered a glimpse into Germany's tricky confrontation with Islamic militants. A child emigre from Lebanon — he declined to give his last name out of safety concerns — he believed in the promise of Germany, he said. An open society and a strong economy meant his family's sandwich shop would provide him with the assurance of a middle-class life.
But he also faced pressure from friends and imams to turn his focus elsewhere. There was a war going on, they said; shouldn't he be joining the struggle?
At a time when deadly attacks in Paris have raised alarm bells over Islamist violence in Europe, Germany faces a predicament. Winning over people like Ali has become the country's highest and riskiest priority. This nation of 80 million must balance a proud democratic tradition with a desire to avoid an attack such as the one on the French satirical magazine Charlie Hebdo, while countering an unexpected increase of anti-Muslim sentiment.
Germany counts nearly as many Muslims as France, with about 4.8 million as of 2010. It received more refugee applications in 2014 than any nation in the world; many came from Syria and Iraq.
The nation also has a strong postwar tradition of tolerance, which has historically made authorities less willing to tackle threats directly. More than in many other European countries, authorities struggle with how to draw the line between religious expression and incitement.
The government has been slowly intensifying its crackdown since the Paris attacks. On Friday, law enforcement raided 11 homes in Berlin on suspicion of Islamic State recruitment and arrested two people, according to police. The action follows similar arrests over the previous week in Cologne and the state of North Rhine-Westphalia.
Meanwhile, leaders and many citizens are anxiously watching the emergence of the hard-core anti-Muslim group Patriotic Europeans Against the Islamization of the West, or PEGIDA.
The organization came seemingly from out of nowhere in recent months. Weekly demonstrations in the eastern city of Dresden hit a high of 25,000 attendees last week. Protesters have rallied around giant crosses colored like the German flag and carried signs reading, "Wir sind Charlie" — We are Charlie.
Many of these gatherings have been met with counter-demonstrations, particularly in bigger cities, where PEGIDA events have been small affairs dwarfed by their opponents.
PEGIDA has proved divisive, and security officials have been concerned that the group could become a target of attacks by Islamist militants. On Sunday, PEGIDA said on its website that it would call off its weekly Monday rally in Dresden, citing threats against its leaders. Police in Germany temporarily banned all rallies until midnight Monday in the wake of the threats.
PEGIDA's rise speaks to the anxiety of a country that was an incubator of the Sept. 11, 2001, attacks via the Hamburg terrorist cell.
Nor is it just the far right that has issued cries over Islamic fundamentalism.
The German hard left, which remains a potent political force, has taken aim at Islamist extremists on ideological grounds.
A leftist group known as Arms for the Kurdish People's Protection Units has backed anti-militant rallies and solicited funds at street corners and at train stations to send weaponry to the Kurdish Rojava region in Syria.
"We feel it is time to stop being pacifist about the threat of Islamic fundamentalism, and the connection between the Middle East and Germany," said the group's leader, a lawyer named Michael Pruetz, as he sat in his offices in the predominantly Turkish neighborhood of Kreuzberg.
Chancellor Angela Merkel has sought to walk a tightrope between laxity and overreaction.
On Thursday, she told parliament that she would take a tough stance against militants.
"Hate preachers, violent deviants who act in the name of Islam, those who support them and the intellectual arsonists of world terrorism will be intensely fought with all legal means available," she said.
But she also had strong words for PEGIDA and its followers. "Any marginalization of Muslims — any unspecified suspicion — is unacceptable," she said.
For many in Germany, the fundamentalist threat evokes the era of the Berlin Wall, when mistrust and ideological divides, even among neighbors, were distressingly common. It has not been lost on some that the locus of the anti-Islamic rallies is not in Muslim-heavy Cologne or Berlin but Dresden, a city heavily associated with the former East Germany and its aggressive secret police.
Many also worry that Charlie Hebdo is increasingly becoming a fig leaf for a separate ultranationalist and anti-immigrant agenda, which had been gaining traction even before the Paris attacks.
Germany's Muslims are largely Turks who came seeking work beginning in the 1960s and Lebanese and Palestinian refugees who fled hostile environments in the 1980s and 1990s.
On the streets of Kreuzberg and the more Lebanese- and Palestinian-skewing Neukoelln, there is a feeling of integration and sometimes prosperity. These neighborhoods remain a far cry from the Muslim ghettos that ring Paris.
In restaurants and bridal-gown shops, owners and residents speak of a country that has offered them opportunity; their biggest concern has often been that their children will forget their homeland. Berlin counts as many as 500,000 Muslims among its population of 3.5 million.
But others say that such a facade can be misleading. As he waited before evening prayers at the mosque NBS in Neukoelln, community leader Assad Nasser, a Lebanese immigrant known as Abu Alla, described a contradictory reality.
"People have jobs and they practice Islam and they live their lives," he said. "But it doesn't feel totally free, like people can really do what they want."
Political rallies outside the mosque and a general skepticism from Christian locals remind them of their foreign status, he said. There have also been incidents suspected to have been religiously motivated, such as a suspicious fire at a radical mosque in Kreuzberg in August. The structure is still badly charred, and signs hang in local sweet shops asking for help finding the culprits.
Still, the relative comfort of Germany's Muslim population has often made non-Muslims wonder why they would travel to Syria to take up arms. At least in France, people say, there are economic motivations.
"I feel sympathy with anyone in the world who cannot practice their religion," said a Christian woman, Kimberley Anschutz, as she shopped at a mall in Neukoelln. "But it seems like life is good for Muslims here. They have good jobs; they can go to mosques and pray. I'm not sure why someone would become a militant."
About 500 German passport holders have fought in Syria or Iraq, according to the International Center for the Study of Radicalization at King's College in London.The French government estimates that more than 1,000 of its citizens have done so.
Experts believe much of the recruitment activity in Berlin is centered on Neukoelln's Rollberg Street. There a string of small Sunni mosques, often not visible from the street, underscores how tricky it is for police to root out militants even if they wanted to.
Driving home the appeal of fundamentalism for many Germans is the rapper Denis Cuspert, known as Deso Dogg. Cuspert had traveled to Syria to join Islamic State and regularly posted videos from there under the nom de guerre Abu Talha al-Almani.
In April, several news outlets reported he had died, but militants in Syria denied those reports, and the rapper's appearance in a beheading video in November made authorities believe he is still alive. Cuspert has become both a prime security threat for German authorities and a cause celebre for the nation's radical elements.
Spokespeople for the country's two main Muslim organizations — the more moderate Central Council of Muslims in Germany and the larger and the more militant Islamic Council for the Federal Republic of Germany — declined to comment for this article.
Yet even as the groups have tried to maintain a low profile, the tensions are becoming harder for many to ignore. "So many people in Germany thought it was just happening out there, many kilometers away," the left-wing activist Pruetz said. "They're finally realizing it's also happening here."