Such preventative measures will reduce the number of attacks and, hopefully, keep them small (no more 9/11s). It's not possible to eliminate terrorism entirely, any more than a "war on crime" can end all crime. It can, however, be kept down to nuisance level.
Terrorism is a very small threat that is designed to look very big. It achieves that goal by attracting massive media coverage that inflates it into an apparently huge threat.
Terrorists want that wall-to-wall media coverage because it may provoke a huge over-reaction that ultimately serves their own purposes. In the case of the current wave of Islamist terrorism, they hope it will build support in the Muslim world for their revolutionary project and ultimately bring them to power.
In the early phase, they wanted to provoke Western invasions of Muslim countries that would drive more Muslims into their arms (as in the case of the 9-11 attacks). Now they are trying to panic Western governments into abusing and oppressing their own Muslim citizens. The basic strategy remains the same, and it has proved very successful.
Without the Western over-reaction to the 9/11 attacks -- especially invading Iraq -- there would be no Islamic State. And they aren't doing too badly with the present attacks either.
Chancellor Angela Merkel knows that, and her response to the Berlin attack was deliberately low-key: "I know that it would be particularly difficult for us all to bear if it turned out that the person who committed this act was someone who sought protection and asylum in Germany."
But Horst Seehofer, the leader of the Christian Social Union, the political partner of Merkel's own Christian Democratic Union, urged the chancellor "to rethink our immigration and security policy and to change it". He was implicitly saying that she was wrong last year to give shelter to almost a million refugees, a majority of them Muslims.
Frauke Petry, the co-leader of Germany's far-right Alternative for Germany party, said it more plainly: "The milieu in which such acts can flourish has been negligently and systematically imported over the past year and a half."
Angela Merkel is now under great political pressure to "crack down" on Germany's Muslims.
As for Donald Trump, he was tweeting within hours: "Today there were terror attacks in Turkey, Switzerland and Germany -- and it is only getting worse. The civilized world must change thinking!"
He says he has a "big brain" but, even so, he should attend the intelligence briefings. The Swiss attack actually involved a Ghanaian-born Swiss citizen shooting Muslims in a mosque.
The US president-elect later expanded on his thoughts: "Isis and other Islamist terrorists continually slaughter Christians in their communities and places of worship as part of their global jihad.
"These terrorists and their regional and worldwide networks must be eradicated from the face of the Earth, a mission we will carry out with all freedom-loving partners."
So how will he do that? Invade more Muslim countries? Round up Muslim Americans and put them in camps, like they did to Japanese-Americans in World War II?
If he did anything like that, he would only be serving the purposes of the Islamist terrorists. He would be, in Lenin's famous phrase, a "useful idiot".
� Gwynne Dyer is an independent journalist whose articles are published in 45 countries.
