Soon after the attacks of September 11, US President George W Bush began to speak of a "war on terror". In the US, and around the world, that sweeping concept resonated with a lot of people in those anxious days.
Times have changed. So on Friday, a senior Pentagon civilian made headlines by evoking an end to the so-called war.
Pentagon General Counsel Jeh Johnson told the Oxford Union in the UK of "a tipping point" at which "Al Qaeda as we know it ... has been effectively destroyed". When that day dawns, he went on, "our efforts should no longer be considered an armed conflict".
Coming from a lawyer, this is a significant distinction. US politicians have often spoken of the "war" on terror as an enduring task for the armed forces. Meanwhile, US government lawyers have worked ingeniously and industriously to find justifications, under domestic and international law, for controversial aspects of the fight against Al Qaeda.
The world knows the consequences. On one hand, attacks on the scale of September 11 have not been repeated. Many smaller terrorist projects have been thwarted. Osama bin Laden was killed. Al Qaeda now seems to have a fractured command structure at best.
But on the other hand, no one can count the dead and injured in Afghanistan and Iraq, or the money spent on destruction there. Western relations with much of the Muslim world have deteriorated greatly and US persistence in using drone strikes in Pakistan and Yemen makes the problem worse. Freelance fanatics, inspired by Al Qaeda tactics, remain a menace and impose enormous security costs on the whole world.
During the Arab uprisings, authoritarian rulers pinned the "terrorism" label on almost every protest. The Assad regime continues to label its own people as terrorists today. In many countries, ancient liberties and personal privacy have been systematically sacrificed to the elusive goal of full security. President Barack Obama promised in 2008 to close the extraordinary prison at Guantanamo Bay, but this stain on US ideals is still in use.
A "war on terror" never did make any sense. To be sure, the era of asymmetrical warfare creates legal and conceptual challenges. But the comments by Mr Johnson - who is sometimes mentioned as a potential US attorney-general - suggest that a more sensible approach is now imminent. War, a "finite, extraordinary and unnatural state of affairs" should give way to a continuous "counterterrorism effort" by US law enforcement and intelligence agencies.
Terrorists are criminals with political motives. Stopping them before they kill, and pursuing them afterwards, are tasks best suited to political leaders and police forces, not to armies and air forces.