Beyond Friday night's carnage in Paris, there were two crucial developments this week. First, there is the emerging realisation in the West that Daesh is no longer just bolstering its Islamic Caliphate in Syria and Iraq but is now planning and carrying out major terror attacks in Europe. Second, to counter this threat, there may be little choice but to co-operate more closely with Russia against Daesh.
Previous attacks ascribed to Daesh - such as the murders at the Jewish Museum last year in Brussels and the killings in January in Paris - were believed to have been carried out by "lone wolves" acting on their own accord.
However, the sophisticated planning required for last weekend's attacks, the use of explosive "suicide vests" and the quantity of weapons employed, leave no doubt that they were the work of a well-organised movement.
As more information comes out, the links between the perpetrators and Daesh figures in Syria are becoming clearer.
This shift of focus on to Europe; the use of the refugee stream as a cover for infiltrating terrorists; and the involvement of French and Belgian citizens, means the West is facing a completely new level of threat.
It also means that Western intelligence and security services will now be co-ordinating more closely and focusing all their resources on this threat.
This international co-operation, however, will raise a thorny question: how can Western governments work together with Vladimir Putin's Russia in the fight against Daesh?
In the space of just two months, Russia has become the country most heavily involved in Syria, along with Iran. While it has claimed to be acting against Daesh, the Russian efforts have been more focused on bombing the rebels fighting the regime of Bashar al-Assad, rather than Islamic State.
Russia's alignment and actions have so far precluded a joint front with the United States, Britain, France and other European countries that are also bombing Daesh in Syria and Iraq.
Until this week, co-operation has amounted to no more than co-ordinating air-strikes to avoid confrontations between Russian and Western jets.
The first sign of this happening were the relatively friendly talks between President Putin and Western leaders - including President Barack Obama and Prime Minister David Cameron - at the G20 summit in Ankara. Following that meeting, Mr Putin instructed his navy to work with France in the Mediterranean against Daesh.
Another sign of the newly joined-up approach are reports of intelligence-sharing between the UK and Russia over the investigation into the crash of the Russian airliner in Sinai nearly three weeks ago, which is now being seen as another Daesh operation against an international enemy.
Assad's future remains a sticking point with Russia, but the embattled Syrian president can allow himself a degree of satisfaction this week at the fact that despite his forces having killed 100 times more civilians than Daesh, the West is now less interested than ever in his removal.
The JC Podcast: Should we be afraid in the wake of the Paris attacks?
