The attacks carried out in Paris last week were neither random nor mindless. They had been planned with some care. Their immediate purposes were clear enough but how they might fit in with any strategy less so. Charlie Hebdo is back with its irreverent pictures of the prophet, and France has declared solidarity with both the magazine and the murdered Jews.
It is difficult to talk about terrorism having a strategy because it is essentially a tactic serving all manner of causes. Since the 1960s ,we have seen murders committed in European streets in the name of socialism, nationalism and Islamism. All these get lumped together under the heading of "terrorism".
In one sense this is the right word, for these acts are literally terrifying and raise questions about the vulnerability of everyone living in open societies, but in another sense it is unhelpful, because it covers too many different political movements and types of operations.
The murder of a politician, a bomb outside a military base, an explosion on a civilian airliner, a random shooting in a shopping mall or even the disruption of a computer network can all come under the same heading. And yet they can be perpetrated by a far leftist, white supremacist, secessionist or modern-day Islamist.
If there is a strategy behind terrorism it is to use a psychological effect, terror, as a means to a political end. It is a deadly form of persuasion, either warning people not to act one way or coercing them to act in another.
Pain can be caused easily but the real challenge for terrorists is to run a campaign, so that one attack follows another and a climate of fear is created.
None of the Islamist groups operating in the West since the start of the century have been able to mount more than occasional attacks, and this limits their impact.
Accepting martyrdom allows individual attacks to be more gruesome but reduces the likelihood of further action. Jews feel fear in France not because of the supermarket attack alone but because there have been a number of incidents, probably uncoordinated but that nonetheless underline their vulnerability.
Dealing with such threats requires deterrence; guards around obvious targets such as schools; good intelligence; and the encouragement of Muslim communities to deny the militants support and sanctuary.
This is not usefully described as "war", although that is the term used by the French government. This leads to the obvious observation that the "war on terror" called by President George W Bush after the 9/11 atrocities has yet to be won. Nor were those called before him by Presidents Reagan and Clinton. The failure to eradicate the phenomenon is hardly surprising given the range of desperate people prepared to use violence.
There are, of course, a number of wars involving Islamist movements at the moment. They are taking place in Iraq, Syria and Libya, Nigeria and Mali, Afghanistan and Pakistan.
There is no supreme commander behind all these campaigns, as each is a response to local conditions, and despite the shared methods and themes, these movements are often in bitter dispute with each other.
This is why it was odd that last week's gunmen claimed to be followers of al Qaeda and Islamic State: the two are deadly rivals in the Middle East, where they compete over the same political space. Both are hostile to the other notorious Middle Eastern groups, Hamas and Hizbollah.
These groups direct their main efforts towards acquiring territory, supporters and political control at home, rather than exporting revolutions to distant communities.
The small cells of militants who perpetrate atrocities in the West are, at most, licensed agents of these large movements or just resentful locals inspired by Islamism. Traumatic as we find their activities, they are sideshows to the main events. Unless there is serious progress against the Islamists in these other wars then we must continue to expect their effects to be felt in the West.
