It is too bad that holiday revelers have to look over their shoulders instead of focusing on the spirit of the season. However, that is the state of the world today, as was made clear by the truck attack Monday in Berlin that killed 12 people and injured dozens more at a Christmas market.

The so-called Islamic State group claimed responsibility for the attack, in which a tractor-trailer barreled into the well-known market by the Kaiser Wilhelm Memorial Church, toppling a Christmas tree, tables and booths and mowing down tourists and Berliners alike. The tragedy was frighteningly similar to the July 14 terrorist truck attack, also linked to IS, that killed nearly 90 people and injured hundreds more at a Bastille Day celebration in Nice, France.

The attacks underscore the terrorists’ interest in “soft targets” -- lightly secured or difficult-to-secure venues that attract throngs of people and present maximum opportunity for casualties. The Berlin incident -- described as the first mass-casualty attack by Islamist extremists in Germany -- also represents an unsettling expansion of the IS footprint.

Such attacks not only induce panic among the population but contribute to political divisiveness, from which the terrorists hope to profit. In this case, critics of German Chancellor Angela Merkel have complained about a slow start to the investigation -- an initial suspect was let go for lack of evidence -- and to her support for immigration.

The US State Department previously had warned traveling Americans to be cautious at events and public places in Europe during the holiday season, and in the wake of the truck attack, German authorities encouraged people to report suspicious activity to a special hotline. Looking over one’s shoulder is the best advice for those who refuse to let the threat of terrorism affect their daily plans, and the need for vigilance applies as much to those enjoying local holiday events as it does to tourists in Germany.

America’s support for Germany, moral and otherwise, will be important in the coming weeks. After a series of terrorist attacks in Paris last year, people around the world expressed support for France with the expression “Je suis Paris” -- “I am Paris.” Now, the Berlin attack gives new meaning to the words John F. Kennedy famously uttered in 1963 in West Berlin: “Ich bin ein Berliner” -- “I am a Berliner.”

(Pittsburgh Post-Gazette)