It’s not a very comforting thought that the Islamic State and al Qaeda show signs of competing to attack their enemies, and that their preferred method is impossible to completely prevent.

There almost certainly will be more attacks in Western cities like the one that killed 130 people in Paris in mid-November; more on targets like the Radisson Blu hotel in Bamako, Mali, on Nov. 20; more suicide attacks in Middle Eastern cities; and perhaps more planes brought down due to breaches at airports with shaky security operations.

There probably will be more cities on lockdown, like Brussels was recently. More hand-wringing (and political grandstanding) about refugees. And more travel advisories, like the one the State Department issued last week. 

It’s understandable that Secretary of State John F. Kerry is talking of wanting to break a narrative of success by the Islamic State.  

Even if they cannot keep up at this pace, it was a surprise that terrorists were able to launch such a cluster of attacks – and worrisome that the Islamic State and al Qaeda are using them to jostle for prestige in the world of extremists.

Al Qaeda, weakened by a long U.S. campaign, has lost status and recruits to the Islamic State. So extremists still loyal to Osama bin Laden’s organization lit up the Internet with praise for the Bamako attack, which was claimed by affiliates of al Qaeda. According to this report, they also argued that it was a smarter attack, in that it targeted non-Muslims (reports on that account are contradictory).

In the past, al Qaeda hurt itself with a campaign of terror that often killed as many Muslims as the non-believers and foreigners it claimed to be fighting. The Islamic State has shown itself to be even more brutal.

The Paris attack in particular, has increased pressure for a much tougher military campaign against the Islamic State, which claimed responsibility for it. Despite the turmoil caused by the downing of a Russian warplane by Turkey, French President Francois Hollande has been pressing for a united front against the Islamic State. While the Islamic State is likely to be diminished, if not eliminated, in the long run, it will take time and more than just arms.

In the meantime, more innocent people will die in terror attacks, and Americans will be among them. They simply may be in the wrong foreign city at the wrong time, like exchange student Nohemi Gonzalez in Paris, or aid worker Anita Datar in Bamako.

But common sense suggests that somewhere, sometime – either due to luck, ingenuity, or a failure of intelligence or police work – a terror plot targeting an American facility or the U.S. itself will escape detection. It almost certainly won’t be of the magnitude of the Sept. 11 attack. But it might it be more ambitious than the work of a “lone wolf” inspired by the Islamic State, which intelligence agency had come to expect.  And as the Paris attack has shown, terrorists using relatively simple weapons can have a devastating impact.

The Sept. 11 attacks used even simpler weapons — boxcutters — but were audacious and complex in their planning. These recent attacks appeared to aim for a relatively easy to replicate combination of planning and firepower – guns and suicide vests.

The Paris attack showed that there is nearly an endless list of potential targets – far too many for police or intelligence services of even a powerful European country to protect. The hotel attack in Bamako is an illustration that a lack of security in poorer countries can make easy targets of the relatively few places where foreign business, government and aid workers are likely to congregate. 

Both cases serve to emphasize that there is an ample supply of young men (and some women) willing to kill civilians — and themselves — or be killed in the process.

What to do? Leaders in the West, in Moscow and in Middle East capitals know most of the elements of the strategy they will employ, and already are using them. 

They include efforts to prevent young people from being radicalized, police and intelligence work to keep tabs on those who might pose a danger, disrupting sophisticated Internet recruiting and communications, shutting off income from oil smuggling, and targeted military action.

But how effective are they? In what proportion should they be used? And how best to coordinate action among countries that are deeply suspicious of each other?

No one has those answers yet. 

They’ll need one more thing: Steady nerves, and an understanding that if they are intent on destroying the Islamic State, they should be prepared for their countries to take casualties as well as inflicting them.