ISIL has today announced a doctrinal shift in its ideology that carries potential historical significance.
In a new 42-minute message posted on Monday, it has called for the first time on its global support to take its fight to foreign shores beyond the Middle East.
Abu Mohammed Ali al-Adnani, the group's spokesman, urges listeners to strike the US and its allies and neither seek permission nor to look for justification.
He calls on them to use any means necessary to cause the enemy injury. The language is formal and clear: "Kill the disbeliever whether he is civilian or military, for they have the same ruling. Both of them are disbelievers."
The US president, Barack Obama, is openly mocked. Adnani refers to him as a "mule of the Jews" and a coward who refuses to fight on the ground but chooses instead to strike from the air. The group insists it did not declare war against Europe and the US but has been forced to act following a US-led international response in Iraq.
ISIL is convinced that the states making up the coalition against them will pay dearly in both blood and treasure. The Arab nations backing the coalition are also singled out for attack. Indeed anyone anywhere who has criticised ISIL is now fair game.
This statement of intent is both significant and chilling in its simple declarative voice.
ISIL wants to carry out a big attack on the soil of the US and its allies. Failing that, the group wants individuals to carry out operations.
Any large-scale organised attack claimed by ISIL will serve two purposes. It will scare people in to going to war while giving politicians the cover to be able to do so. The September 11 attacks of 2001 and the ensuing wars in Iraq and Afghanistan are the textbook example of that. As in the past, this new venture may mean coalition boots on the ground.
ISIL want to engage in a ground war against coalition troops. The reason for that is simple. Their recruitment, they hope, will go through the roof as young men the world over flock to Iraq and Syria to fight and kill enemy soldiers.
When it comes to writing the history of ISIL, Adnani's statement will be seen as one of its defining moments. This is the moment when a declaration of war was made against the US and its allies.
Who's listening to ISIL?
However, is anyone paying attention?
Muslim opinion is quickly turning against the group, a point Adnani dismissed in his statement.
Will ISIL encourage individuals to commit murderous crimes in the name of religion? The Australians claim they've had a taste of ISIL's successful foreign recruitment already. In recent days there have been several arrests of young men suspected of being inspired by ISIL. Anti-Islamic feeling in Australia is now on the rise as a result.
So, as much as this statement is an act of war, it's also an opportunity to dissect and analyse what the group is thinking.
Condemnation of this statement will be swift as the content of the message proposes neither a solution nor a way out it simply offers a lust for spilt blood. The group's limited appeal will be exposed if Muslims in the US, Europe and beyond ignore this call to violence.
However, all it takes is one individual to commit a crime, and a whole religion will come under vocal attack by the security services, the media and society at large.
ISIL understands this and hopes to achievement such an outcome. They want Muslims in "enemy" countries to be criminalised and marginalised in the hope that they rise up in anger.
This is a group with nothing to lose. The "caliphate" it has created is ill-defined and lacks credibility. Few Muslim groups have voiced support for ISIL. Now, it is under aerial bombardment fby a US-led coalition, a threat it both acknowledges and feigns to ignore by saying:
"We have no way to deal with their airplanes. Oh God what you have said is true. Do not weaken and do not grieve. You will be superior if you are true believers."
ISIL have thrown down the gauntlet, not just to the US and its allies, but for Muslims living in those countries. What happens next and who responds will be of crucial importance.
Follow Imran Khan on Twitter : @AJImran