The following are possibilities.
It is clearly extremely early in the investigation. But the best guide to who might be behind the attacks in Paris is earlier violence in France or involving French citizens elsewhere in Europe.
One scenario is an attack directly organised and controlled by the Islamic State from somewhere in Syria and Iraq. Previously, Isis have merely called on local followers in Europe to act alone. However, following the bombing of the Metrojet over the Sinai earlier this month, it is clear the threat from Isis is evolving very fast and the group is the obvious suspect. This new attack is consistent with a steady escalation over 18 months of strikes against international targets.
Latest coverage of the attacks across Paris that have left at least 128 people dead
Read moreA team could have been sent into France, or recruited in France, or both, and then carefully managed from overseas. There are an estimated 520 French citizens fighting in Syria and 250 “returnees”, according to latest official estimates.
A second scenario would be something closer to the attacks in Paris 10 months ago. This could involve either the Isis or al-Qaida, the veteran organisation once led by Osama bin Laden. It could indeed involve both, as was the case in January. That strike involved three local gunmen. One swore allegiance to Isis but had never had any direct contact with the group. Two others were brothers, of whom one was tenuously connected to al-Qaida in Yemen. It was this affiliate of the group which claimed responsibility for the killings at the office of satirical magazine Charlie Hebdo.
Al-Qaida, it is worth remembering, is keen to regain the pre-eminence among the jihadi movement it has lost to Isis. A spectacular attack in Paris would be one way to do this.
The third scenario would be local actors, entirely alone. France has a large pool of alienated, angry, frustrated young Muslim men, and there have long been many informal networks of extremists, violent and non-violent. Most are oriented towards sending people to Syria, however, not attacking at home.
Few attackers in recent years have been genuine “lone wolves” either. Most – such as Mohammed Merah, who shot seven people in Toulouse and Montauban in 2012 or Mehdi Nemmouche, who killed four at a Jewish museum in Brussels – had links to a group overseas. We have seen that untrained attackers can kill in a clinical, cold-blooded way that appears professional even if they have not been properly trained, but the kind of co-ordination, preparation and resources needed for an operation such as that seen on Friday makes it unlikely to have been the work of amateurs alone.
Few terrorist tactics or targets are ever entirely original, but a combination of different elements can often be innovatory. The tactics adopted in Paris have been seen in many earlier strikes, but particularly recall those used by attackers in Mumbai, India’s commercial capital, in 2008. They hit hotels, cafes, a Jewish centre and commuters. Since then, security services have worried about a similar operation in the west. There have been several scares.It is possible that the targets hit last night were chosen to send a particular message. They were not heavily protected embassies, tourist sites, luxury shops, or museums. Except for the Stade de France, they were modest venues in Paris’s less exclusive, more multicultural eastern neighbourhoods. This may have been a deliberate act of selection – or may simply be because the area well known to the attackers.
We will update as more information unfolds.