When US forces killed Osama bin Laden in May 2011, it marked the end of al-Qaeda as a unified global force. Straining under the losses caused by relentless US drone strikes, the old guard of al-Qaeda was already struggling to maintain control over the organisation it created. And when Osama bin Laden died, al-Qaeda as we knew it died with him.
But in its place, a new, arguably more dangerous version of al-Qaeda has taken shape. It is one that pays lip-service to al-Qaeda ideals and draws on the essential elements of al-Qaeda methodology and recruitment. It is, however, far less predictable, with its many constituent elements eager to go their own way.
''Al-Qaeda now is a franchised organisation. They have branches in most of the Middle East and most of the Islamic world, and it is growing,'' says Abdel Bari Atwan, the author of The Secret History of Al Qaeda and After bin Laden: Al Qaeda, The Next Generation.
''Al-Qaeda used to be a pyramid-built organisation with Osama bin Laden at the top,'' he continues. '''Now you have a flat, loose organisation with several heads and several headquarters. It makes them extremely dangerous.''
The new breed of Islamist militants uses many classic al-Qaeda strategies. All, for example, thrive in areas where there is no effective government control. There, free from interference, they set up training camps and operational headquarters.
They also provide the quasi-governmental services that are such powerful recruiting tools among those for whom national or local governments are as distant as foreign powers.
Other elements, however, represent significant departures from mainstream al-Qaeda operations. Where al-Qaeda under Osama bin Laden was able to draw on its leader's vast personal fortune, the new groups have been forced to find new ways to generate income.
As each does so, each becomes more independent, to the extent that operational decisions are now more often made in Mogadishu or Nigerian city Maiduguri than they are in al-Qaeda hide-outs in Pakistan or Afghanistan.
Where new militant Islamist groups also differ is in the enemy they have chosen to fight. While the differences may be subtle, the primary target for al-Qaeda under Osama bin Laden was Western interests across the globe. Most new groups direct their attacks on governments in the regions in which they operate.
Driving these changes in Islamist militancy may be differences in philosophy and operational strategy. But there is also a generational shift at play here.
''Like the old saying goes: The revolution devours its own,'' says Jerome Drevon, a fellow at the Swiss National Science Foundation and who specialises in Islamist movements. ''What we are seeing is a generational split between older jihadis who have learned pragmatic lessons … and a younger, more brutal generation who don't believe in or haven't lived long enough to learn those lessons.''
Or as Abdel Bari Atwan puts it: ''The next generation is more lethal, more dangerous.''
Whatever the reason, the localisation of the war on terror has broadened terrorism's reach in frightening ways.
By flying under the radar of international attention, militant groups are able to plant deep roots in the local soil in impoverished regions. Thus established, these inheritors of al-Qaeda's legacy can grow to a point where they are capable of outrages on a scale worthy of international attention. Some have even proven that they can take over large swaths of territory, from Mali and Somalia to Syria and Iraq.
And by the time they reach this stage, of course, they are no longer a purely local concern. Here are some of the new major faces in international terrorism.
Islamic State in Iraq and the Levant (Syria and Iraq)
If ever confirmation was needed that al-Qaeda in the post-bin Laden era had lost control over the forces of global jihad, it would come in Syria and Iraq.
In the early days of the Sunni insurgency, the leader of al-Qaeda in Iraq, Abu Musab al-Zarqawi, was pulled back into line by al-Qaeda's leaders, told to focus his attacks on Western targets, rather than on enemies within the Muslim world. Although unhappy, Zarqawi accepted the rebuke.
After the deaths of both Zarqawi and Osama bin Laden, however, the situation changed. Ominously, the new guard of leaders in Iraq pushed for a more extreme position on religiously sanctioned killings than even Ayman al-Zawahiri - a man accused of being one of the masterminds behind the September 11 attacks and bin Laden's successor - could accept.
In April 2013, Abu Bakr al-Baghdadi, the leader of the Islamic State in Iraq and the Levant (known as ISIL, or sometimes simply Islamic State), launched a hostile takeover of the al-Qaeda-backed Nusra Front in Syria. When Zawahiri ordered Baghdadi to return to Iraq, the latter thumbed his nose at al-Qaeda's most senior elder statesman, replying that he had ''chosen the command of God over the command that contradicts it''.
It was a stunning rebuff, and the most powerful sign yet that power had shifted definitively away from the old guard. Most remarkably of all, al-Qaeda had been forced to disown one of militant Islam's most significant groups for being too extreme. ISIL now controls much of northern Syria and northern Iraq, ruling over far more territory than al-Qaeda under Osama bin Laden ever achieved.
And in a further worrying sign for the future, Baghdadi's stance is, according to Richard Barrett, former head of counter-terrorism at MI6, striking a chord with a new generation of Muslims in Western countries.
''There is a wellspring of disillusioned Muslims in Western Europe vulnerable to radicalisation,'' he says. ''They are looking for a leader who doesn't sit back and cogitate but who acts on his beliefs, who understands their feelings of marginalisation.''
Such is the face of modern terrorism, a new world in which the unpredictable forces of militant Islam gather both support and territory wherever they put down roots, and in the process widen their appeal to disaffected Muslim youth across the globe.
Boko Haram (Nigeria)
Boko Haram signifies another important departure from al-Qaeda as it existed under Osama bin Laden.
Boko Haram began as a small Islamic sect that attracted a militant band of jobless youth in the early years of the 21st century. In the impoverished and predominantly Muslim north-east of the country, rampant corruption, unequal distribution of the country's oil wealth and resentment against the country's Christian-led government played into Boko Haram's hands.
Even so, Boko Haram was small-scale, a local sect whose leader even served as a minister in the local Borno state government until 2009.
The turning point came on July 12 of that year when security forces clashed with Boko Haram mourners at a funeral. When the government refused to apologise for the slight, Boko Haram launched a vicious rebellion in which all symbols of the Nigerian state, as well as Christian communities, were considered legitimate targets. That war continues today.
Born in local conditions, focused on local targets, Boko Haram shares little with al-Qaeda of old beyond religion and a willingness to wreak havoc in Islam's name. That Boko Haram in Nigeria recently expressed its support for ISIL and not al-Qaeda provided further confirmation of this seismic shift to militant Islam's new guard.
More than that, Boko Haram highlights how security and intelligence forces have yet to understand the new reality.
By deliberately slighting Boko Haram in 2009, the Nigerian authorities committed a fundamental error - dismissing grievances that carried great importance in the local world within which Boko Haram moved. They also imagined that a military solution was possible.
And in an important lesson for anti-terrorism experts across the globe, the wider international community also missed the early warning signs of Boko Haram's rise. By the time that Boko Haram shot to international infamy by kidnapping more than 200 girls (who are still missing) in April this year, the sect was already a major threat to regional security and much of northern Nigeria had long before gone up in flames.
Boko Haram has launched three attacks into Cameroon since Friday killing at least eight people and kidnapping the wife of Cameroon's Vice-Prime Minister.
Al-Qaeda in the Islamic Maghreb (North Africa)
The fragmentation of al-Qaeda's legacy actually began in North Africa, long before the emergence of ISIL and Boko Haram.
With attention - both media and military - focused on Iraq and Afghanistan since the 1990s, the empty spaces and weak governments of the Sahara and the Sahel in North and West Africa provided fertile ground for the next generation of militant Islamist fighters.
Al-Qaeda in the Islamic Maghreb (AQIM) was officially born in Algeria in 2002. Its genesis, however, dates back to 1991 when Islamists won an overwhelming majority in the first round of elections, only for the military to cancel the polls and seize power.
In the brutal, decade-long civil war that followed, Islamist fighters saw their ranks swelled by returning, battle-hardened Algerian veterans from the war in Afghanistan. Such was the dominance of al-Qaeda in the post-September 11 era that AQIM's leadership sought legitimacy by association, and Algeria's disparate group of Islamist militias united under the banner of al-Qaeda.
Their control over remote stretches of the Sahara provided at once a refuge and a revenue stream. First they muscled in on lucrative and long-standing trans-Saharan smuggling routes.
Then, in 2003, AQIM kidnapped 32 Western tourists in the Algerian Sahara. When the hostages were released, reportedly after Germany and other European governments paid a multimillion-euro ransom, an industry had been born. In the decade that followed more than $80 million in ransom money flowed into AQIM's coffers.
With weapons from Libya moving freely across the Sahara after the fall of Libya's Colonel Muammar Gaddafi, AQIM and its affiliates seized control over northern Mali in 2012. Thus it was that AQIM became the symbol of the new al-Qaeda - still affiliated with and claiming allegiance to al-Qaeda's spiritual home in west Asia, but no longer reliant on the old guard to make territorial gains and attract international headlines. Not since the days of Taliban Afghanistan had they wielded so much power.
French forces may subsequently have driven them out, but AQIM's successes were a sign of things to come.
Al-Shabab (Somalia)
Like AQIM, al-Shabab proved adept at occupying and exploiting vast tracts of territory beyond the control of a central government. Also like AQIM, al-Shabab, which was able to draw on the proceeds of pirate activities off the Somali coast, used the classic al-Qaeda strategy of framing their call to arms in terms of a common, infidel enemy.
In Somalia, there was no shortage of candidates. The ill-fated US occupation of the country in 1992-93 planted the seeds of anti-Western sentiment. But it was the invasion of Somalia by Ethiopia in 2006 and Kenya in 2011 that gave real impetus to al-Shabab.
Far from defeating al-Shabab, these invasions served as rallying cries for disaffected Somali youth. The result was ongoing attacks on Kenyan-held areas inside Somalia, as well as targets within Kenya itself, from the Westgate Shopping Mall in Nairobi in September 2013 to the attacks along Kenya's coast in June this year.
By maintaining a strict focus on its own theatre of operations, al-Shabab is among the first offshoots of al-Qaeda to indicate the future direction of Islamist terrorism - born in local conditions, in the negative space left by the failure of regional governments, their first priority is regional rather than global power.
Crucially for al-Shabab's aims, in Kenya alone there are more than 2.5 million Somalis, many of whom inhabit the Nairobi suburb of Eastleigh, known locally as ''Little Mogadishu''. Many have also been harried by the Kenyan authorities in the wake of the Westgate attack and shut out from the opportunities presented by Kenya's faltering economy.
Al-Shabab has in this way, too, come to symbolise what security and intelligence officials are calling ''al-Qaeda 2.0''. Noting the change, Admiral Eric T. Olson, the former commander of US Special Operations forces, warned that al-Shabab would become the face of Islamist terrorism, relying more on ''more Westernised'' recruits, ''dual-passport holders'' and ''fewer cave dwellers''.
Al-Shabab may have formally sought to join al-Qaeda's ranks and obtain the blessing of al-Qaeda's leadership in 2012. But al-Shabab (whose name translates as ''the youth'') has little need for the imprimatur of ageing al-Qaeda leaders, having themselves long before become the free-wheeling symbols of a post al-Qaeda world.
Anthony Ham is a Melbourne journalist.
