Among the many terrible facts about the bloodshed in Paris, one stands out.
No terrorist group has ever previously inflicted the combination of attacks claimed by the Islamic State of Iraq and the Levant (Isil).
The carnage in Paris must be placed alongside other recent events for its real significance to become clear. True enough, Isil's claims of responsibility should always be treated with caution, but if they are accurate, then consider what its operatives have inflicted in the space of just 13 days.
Since Oct 31, Isil has destroyed a Russian passenger plane over Egypt, wrecked a street in Beirut using two suicide bombers, and brought terror to Paris by carrying out near simultaneous assaults on at least six separate targets across the capital.
Assuming its claims are true, Isil has carried out three complex and ambitious acts of mass murder in three different countries - spread across two continents - in less than a fortnight. Along the way, its terrorists have killed 393 people from nations as disparate as Lebanon, Ukraine, France and Russia.
When David Cameron said that events in Paris showed Isil's appetite for "mass casualty attacks" and a "new degree of planning and coordination", he was making the point in mild terms. There is simply no precedent in the modern history of terrorism for the rapid succession of havoc that Isil appears to have wrought.
The group's recent attacks are unique in several respects. The fact that they happened quickly and in far flung countries is important, but not, in itself, decisive. Al-Qaeda never actually struck three targets in three countries in 13 days, but Osama bin Laden's followers might have been capable of doing as much in their heyday before 2001 - provided, that is, we are talking about the kind of bomb attacks that the network had made its speciality.
What makes Isil's onslaught unique is how different the three operations were - and how each demanded a particular range of skills.
Most terrorist groups come to specialise in one method of bloodshed. Under bin Laden's leadership, al-Qaeda developed a near obsession with destroying civil airliners - a compulsion that reached its apogee on September 11 - or planting large bombs in unsuspecting capitals. For the first two decades of its existence, Hamas concentrated almost exclusively upon suicide bombings in Israel.
The events of the last fortnight appear to demonstrate that Isil has mastered all of these black arts and more. The destruction of the Russian airliner showed that its operatives can subvert airport security and infiltrate explosives on board a passenger plane.
The deaths of 41 people in Beirut last Thursday once again displayed Isil's ability to inflict a tragically familiar brand of terrorist attack, namely a double suicide bombing in a Middle Eastern capital.
And then came Paris. On Friday night, Isil's terrorists used automatic weapons and bombs to carry out an assault which appeared to owe as much to the "urban guerrillas" of Seventies Europe as to the Islamist brand of nihilism.
Four decades ago, young Germans and Italians joined the Red Brigades or Baader-Meinhof gang and fought gun battles in city streets. They took hostages and murdered passers-by, causing Italians to use the term "Years of Lead" for that era of their history, for the empty bullet casings scattered in the streets after every incident.
Isil's terrorists followed a similar modus operandi in Paris, except that they focused solely upon killing innocent bystanders - not police officers or government officials - and their murderous exertions were ended only by their own deaths.
But the conclusion is unmistakable: when it comes to destroying a plane, taking hostages, dispatching suicide bombers to Beirut, or running amok in a European capital, Isil's operatives can do all of the above in quick succession. They have shown their mastery of the full spectrum of terrorism in a way that no group - not even al-Qaeda - has ever done before.
How has this happened? The answer probably lies in the unique opportunities provided by Syria's civil war. This catastrophe gave Isil the chance to seize a lawless and ungoverned territory not in remote Central Asia - where al-Qaeda found a haven in Taliban-ruled Afghanistan in the Nineties - but near the borders of Europe. Isil's domain is barely a two-hour drive from Turkish cities like Gaziantep, which are served by cheap flights to London and Paris. This helps to explain how Isil has managed to attract thousands of European Muslims - including about 750 from Britain - to what it claims is the only genuine "Islamic State" in the world.
Here, the recruits can train and arm themselves and test their strength on the many battlefronts where Isil fighters are engaged against their enemies. They can be fully indoctrinated and then sent back to Europe, carrying passports that allow them complete freedom of movement across a continent that was, until recently, largely without border controls.
In the process, Isil's goals and tactics have clearly changed. Once, its central purpose was to build a new country where the most puritan and extreme interpretation of Islam, complete with slavery and beheadings, would hold sway.
The terrorists would kidnap and murder any Westerners within reach of their domain - hence the murders of hostages - but they did not appear to share al-Qaeda's consuming obsession with striking Western capitals. The infusion of thousands of enthusiasts carrying Western passports seems to have changed that. With such an influx of volunteers, the temptation to go on the offensive and attack what Isil calls the "crusader states" appears to have been too great to resist.
Syria's civil war handed Isil the chance to master every aspect of terrorism on a metaphorical silver platter. The events of the last fortnight show that it has grasped the opportunity with bloodstained hands.