So is this war? In a way, yes. French armed forces have been involved in combat operations against Islamist radical groups in northern Mali for almost three years. Opinions polls show wide popular support for these foreign operations. In fact, this is probably the only issue on which there is domestic political consensus. Unlike their British neighbors, the French bear no trauma from the Iraqi war, having refused to take part in it — for good reasons, it turns out. Though over the weekend some politicians called on the government to review its strategy in the Middle East, not a single one suggested that France should put an end to its military involvement in the region.

But fighting a “terrorist army” at home is a different kind of war. Americans have experienced this, except that the enemy they fought after 9/11 was foreign. In Europe, the terrorists we are confronted with are our fellow citizens, born and bred in our societies. “This is a new operational mode,” Interior Minister Bernard Cazeneuve said Sunday on French television, “a group in Syria directing French people in Belgium to commit attacks in France.” Suicide bombers used to be a Middle East phenomenon; the Middle East war has now spread to our soil.

So if this is a war, it will require different tools, and nobody knows whether the French are prepared for the consequences, or the cost. For most Europeans, war was a conflict between states that had either territorial or ideological claims, fought by regular armies. It had a starting date and an end date. It belonged to previous centuries. War nowadays, writes the political philosopher Pierre Hassner in a recent book on the subject, “La Revanche des passions” (“Revenge of the Passions”), “has been relegitimized in the form of jihad, of global war on terror, or with the aim of promoting democracy.”