The massacre on Wednesday at a satirical magazine in Paris that had published cartoons of the Muslim prophet Muhammad is the worst, but only the latest, outburst of terrorism in France in recent years.
Citing French television footage, The Associated Press reported that the gunmen shouted "Allahu Akbar!", Arabic for "God is great!", as they fled the headquarters of Charlie Hebdo after killing at least 12 people. President François Hollande called it a terrorist attack.
It was only three years ago, in November 2011, that the same magazine's offices were damaged by a firebomb thrown through the window. The magazine had just announced a special issue called Charia Hebdo, a play on Shariah law.
And in 2012, a Frenchman of Algerian descent claimed responsibility for killing three Jewish schoolchildren, a rabbi and three paratroopers in Toulouse. The attacker, Mohammed Merah, had espoused radical Islam and claimed to have links to al Qaeda.
The French military has been fighting Islamic militants in Mali, a former French colony. And last year France was the first country to join American-led airstrikes against ISIS in Iraq.
"It's very, very dangerous and very scary in France," Christopher Dickey, the foreign editor of The Daily Beast, told NBC's TODAY. "It's been engaged in a lot of countries where it's up against Islamist militants. The question was, would they strike back and would they go after a soft target or a military kind of target."
He stressed that it was not clear who was responsible for Wednesday's attack.
Less than three weeks ago, a man shouting "Allahu Akbar!" plowed his car into a crowd in the city of Dijon, injuring 13 people. Prosecutors later said that the man had a history of psychiatric problems.
The prime minister said at the time that France had "never before faced such a high threat linked to terrorism." In the moments after Wednesday's attack, Hollande said that other terror plots had been foiled in recent weeks.
Also in December, French police shot and killed a man who stabbed three officers in a police station. The man was also shouting "Allahu Akbar!"
Josh Earnest, the White House press secretary, told MSNBC's "Morning Joe" on Wednesday that the French are "stalwart allies" in the fight against ISIS, including the need to stop foreign fighters.
"Throughout this campaign, the French and international community has confronted the threat from ISIS," he said. "We know they won't be cowed by this act."