Police officers stand guard at the scene where a truck crashed into a Christmas market Monday, close to the Kaiser Wilhelm Memorial Church in Berlin. (Clemens Bilan/European Pressphoto Agency)

The claim on the official Amaq media channel was short and distressingly familiar: A “soldier of the Islamic State” was behind yet another attack on civilians in Europe, this time at a festive Christmas market in Berlin.

The accuracy of the claim remained in question Tuesday as German authorities searched for both a suspect and a motive behind the deadly truck assault on holiday revelers. But already it appeared that the attack had achieved one of the Islamic State’s stated objectives: spreading fear and chaos in a Western country in hopes of sharpening the divide between Muslims and everyone else.

Terrorism experts likened the claim to a declaration of all-out war against a country that until now had seen little of the terrorist violence that has rocked its ­Francophone neighbors. Germany, with its large Muslim community and recent history of political discord over Muslim immigration, has long been viewed by the militant group as an important strategic target, despite the country’s reputation for tolerance.

Islamic State officials in recent months have urged supporters to carry out attacks in Germany by any means — including using nontraditional weapons such as trucks — with the aim of creating an anti-Muslim backlash in ­Europe’s biggest democracy. The resulting crackdown would benefit the Islamic State, the group argues, by dividing Europeans and driving wavering Muslims into the jihadists’ corner.

(Victoria Walker,Peter Stevenson/The Washington Post)

“The very fact that Germany has played only a minor role in anti-ISIS efforts — but is the most important state in Western Europe — may make it a good place to sow division within the Western alliance,” said Paul Pillar, a former CIA counterterrorism official and a senior fellow at Georgetown University’s Center for Security Studies. “The specter of Muslim refugees and immigrants turning on their hosts, in a country that has accepted an especially large share of such migrants, may intensify anti-
immigration sentiment not just in Germany but also elsewhere in Europe.”

The Islamic State’s claim of responsibility came nearly 24 hours after the attack on the Breitscheidplatz square, where an unknown assailant drove a truck through a crowded Christmas street festival, killing 12 people and injuring nearly 50.

German police initially detained a Pakistani asylum seeker who had fled the scene, but authorities later released the man after concluding that he had not been involved.

The group’s statement simply attributed the attack to a “soldier of the Islamic State” but gave no details about the attacker. In the past, the group has claimed credit for terrorist acts committed by individuals who were inspired by its propaganda but had no direct ties to the organization or its members.

Some counterterrorism experts treated the claim with skepticism, noting the lack of authenticating detail as well as the truck driver’s behavior during and after the attack. For example, unlike previous incidents in which the perpetrators seemed to have expected death or “martyrdom,” the driver of the Berlin truck fled the vehicle and escaped by blending in with the crowd.

“The easiest thing to say is, ‘It’s ISIS,’ but if you’re conducting an investigation, you have to ask all sorts of questions and explore all sorts of possibilities,” Ali Soufan, a former FBI supervisory special agent who investigated terrorism cases, said, using another name for the Islamic State. “You have to follow the evidence, and it seems interesting to me that we’re seeing some stuff that we haven’t seen before.”

Lorenzo Vidino, director of the program on extremism at George Washington University, said the driver’s behavior suggested that the attack may have been inspired by jihadist ideology but was not connected operationally with the Islamic State.

The choice of Germany may have been simply a matter of opportunity or — if the Islamic State was truly involved — a strike against a strategically important target.

“Germany is a target for obvious reasons,” Vidino said. “One of them, paradoxically, is its open-door policy towards Syrian refugees. From ISIS’s perspective, that policy takes away the natural citizens of the caliphate, showing its bankruptcy. Every refugee that is welcome in Germany is a living testament of how most Muslims want little to do with ISIS’s project.”

On a more strategic level, he said, the attack helps fulfill the group’s core objective of widening the gulf between Muslims and non-Muslims.

“For any Western country they target, jihadists want more polarization between Muslims and the rest of the population,” Vidino said. “An attack on such a cherished, popular and Christian tradition definitely works in that direction.”

The Islamic State’s propaganda machine has produced hundreds of messages in recent months urging followers to carry out terrorist strikes abroad without waiting for specific instruction or coordination. The volume of such messages has increased in recent weeks as the terrorist group has suffered a string of military defeats in its self-declared caliphate in Iraq and Syria.

In November, the organization’s French-language media outlet called on European Muslims to replicate the July 14 terrorist attack in Nice, France, in which a French Tunisian ran over scores of people along a crowded seaside promenade, killing 86. The posting featured a Muslim man vowing to “take my truck and go forth, towards my enemies upon whom I will inflict a true punishment, until they are afflicted with grief.”

Islamic State officials have explicitly sought to link such attacks to the larger goal of making Europe intolerable for faithful Muslims. A 2015 article in the group’s English-language magazine, Dabiq, warned that the terrorists would soon begin targeting the West with the aim of deliberately provoking a backlash against Muslims living there.

“Muslims in the West,” the article said, “will quickly find themselves between one of two choices: they either apostatize and adopt the [Western] religion . . . or they emigrate to the Islamic State and thereby escape persecution.”