LONDON – The latter part of September was deeply depressing: bombings in Iraq, scores dead in a Pakistani church, a new alliance of extremist Islamic brigades formed in Syria and the siege of a top-end mall in Nairobi, with at least 72 people killed by militants from the Somalia-based al-Shabaab group.

Twelve years after the 9/11 attacks, our tolerance for such violence is higher. But every few months, there is an incident that is sufficiently close to home, literally when a soldier is killed on the streets of London, or figuratively when weekend shoppers are targeted, to provoke the existential dread that is the aim, by definition, of terrorism.

There are, however, several reasons to be more cheerful about the future than last month’s events might suggest.

First, the al-Qaida central leadership is, most analysts agree, very much weaker than before. The death of Osama bin Laden crippled an organization that owed much of its influence to its media image. The current leader, Ayman al-Zawahiri, is an effective strategist and organizer but has nothing of his predecessor’s charisma.

Second, the overarching strategic objective of al-Qaida was to radicalize and mobilize tens of millions of Muslims and to terrorize the West to achieve a radical rearrangement of, if not the world, then certainly the Middle East, much of Asia, some of Africa and, arguably, parts of Europe. This has not happened.

Realistically whatever the chill consequences of the desperate turn taken by the Arab Spring, it is still difficult to envisage the establishment of an Islamic caliphate stretching from Pakistan to Morocco in the next decade or so.

Third, though the fate of the Muslim Brotherhood in Egypt has been understood by many as a clear message that Islamist aims will not be achieved through the democratic process and will have pushed some, particularly locally, toward violence, al-Zawahiri himself has recognized the continued marginalization of extremists in much of the Muslim world. He recently issued guidelines that urged local al-Qaida-linked groups to avoid earlier mistakes that had so alienated local communities.

Fourth, the phenomenon of Islamic militancy today is more fissured and fragmented than at any time since the late 1990s, when al-Qaida began to draw together some of the myriad fractious groups then operating across the Islamic world. This is true at local levels, too — in Pakistan, in Syria, in Iraq, in the Maghreb, in the Sahel. It is certainly true in Somalia.

It may well be that Ahmed Abdi Godane, the leader of a splintered and weakened al-Shabaab group, decided to launch the strike in Nairobi to establish his own authority as leader by an action no rival would contemplate. Such “internal competition” is typical of extremist groups, as multiple recent studies of “jihadis” by security services have established. Palestinian groups in the 1970s or anarchists in the 19th century were no different.

Fifth, the territory held by militant groups looks impressive on a map but is largely composed of places that no one else wants: large tracts of remote mountains or deserts for the most part. Al-Shabaab is one of the few groups, outside Syria, that controlled decent sized towns. Another plausible reason for the Nairobi attack is that Godane hoped that a new international profile would bring in cash from the wealthy donors in the Gulf who continue to fund extremism. Al-Shabaab lost significant revenues when forced out of the port of Kismayo by Kenyan troops last year.

Finally, intelligence services are more worried now than they were a year or so ago but much less concerned than they were back in the darkest days of 2003-2006 when bombs were going off from Casablanca to Jakarta, hundreds were dying in Europe, Iraq was in total chaos, Afghanistan was deteriorating fast, and senior spooks in London looked gloomily into their pints and spoke of “the wheels coming off.”

Now for the reasons to be less sanguine. First, al-Qaida tried repeatedly to graft a global ideology onto individual local struggles. This project usually failed because the vision of the group did not sufficiently respect local circumstances. Bin Laden believed that spectacular attacks broadcast to hundreds of millions could replace years of work on the ground. Events proved otherwise.

But Godane seems to be trying to plug a local struggle into a global ideology. Being Somali himself, Godane is better placed to know what will work in his homeland. That he is less acquainted with geopolitics doesn’t really matter.

A similar project has already been relatively successful in Yemen, where the militants that Western intelligence agencies believe pose the greatest threat to the West appear solidly rooted.

So far however, most militant groups have remained obstinately local in their focus, if not their rhetoric. The vast proportion of all violence involves attackers striking close to where they live. They don’t get on planes — either to destroy them or to fly to where they can destroy something else — very often. But clearly this could change.

Second, the territory held or contested by militants is certainly unattractive, but is often of strategic value. The Sinai, parts of Syria and Yemen, the Afghan-Pakistan border regions, southern Algeria are all remote but critical bits of real estate on the global map. That is a genuine concern and can prompt clumsy, often counterproductive, responses from local and Western powers.

Third, Godane emerged after less extreme figures were killed off by U.S. drones. The elimination of leaders can be extremely useful but has unpredictable consequences. Assassination is now seen as a key weapon in the struggle against extremism in Western capitals at the moment. But it is a tactic, not a strategy.

Fourth, Islamic militancy, a phenomenon with deep historical roots in social, economic, religious, cultural and political factors in the Islamic world and in the Islamic world’s relationship with the West, appears durable. The recent phase dominated by al-Qaida lasted roughly from the early 1990s to 2011, peaking with the 9/11 attacks. A previous phase lasted from the late 1960s to the end of the 1980s, another 20-odd-year period, and peaked with a wave of extremist activity between 1979 and 1981. If this new dynamic, chaotic phase follows this pattern, we are looking at another two-decade cycle with a peak in about 2022, something the security planners of the Qatar World Cup might like to chew over.

What is clear is that we cannot defend every Westgate in the world against terrorist attack. Indeed, we cannot defend even a tiny fraction of them. If it is unlikely there will be more 9/11s, it is certain there will be more Westgates — as there will be more Mumbais, Londons, Madrids and Balis. We can mitigate the threat, but we cannot eliminate it. Hyperventilating, though inevitable, will not help. We are just going to have to live with it, and for some considerable time to come.

Jason Burke, South Asia correspondent for The Guardian and The Observer, is the author of “The 9/11 Wars.”