The Catalan crisis has escalated. Both sides are taking the nuclear option.
The Catalan parliament is declaring independence.
The Spanish Senate is authorising Article 155, allowing the use of "all means necessary".
The unity and future of a modern European nation is hanging in the balance.
Spanish Prime Minister Mariano Rajoy is determined to stop Catalonia before separatists in the Basque Country and Galicia try to follow suit.
Legal expert Rafael Arenas says Spain is sailing into uncharted waters.
He said: "We are in a crossroads. The crossroads is that the nationalists here in Catalonia are trying to force the independence outside the law.
"The international law and the Spanish law and the government has arrived at the point where there is only one tool to stop this situation and that is Article 155."
Mr Rajoy's government has the power of the state, its military and the law on his side. But he must choose carefully how to use them.
He can now impose direct rule, remove Catalonia's cabinet and demand its institutions of government follow directions from Madrid.
All well and good in theory.
But in practice? Can the Spanish government actually enforce its will against the massive show of people power we have seen on the streets of Barcelona and elsewhere in the region?
If separatist supporters choose to defend the buildings of the Catalan government and protect their government, will Madrid force a confrontation?
They've proven capable of defying central government organising a referendum where millions voted.
And they are now threatening mass civil disobedience.
The loyalty of Catalonia's police force could be crucial as Madrid tries to enforce its writ across Catalonia and take over its government. That can by no means be taken for granted.
In the end Madrid's greatest weapon may be time.
Knowing the longer this goes the more Catalonia's economy is damaged.
Legal expert Eduardo Barrachina told Sky News the crisis is already hurting the region's finances.
He said: "The mere thought of independence has prompted 1,500 companies to abandon Catalonia and I'm including Catalonian companies that had been in Catalonia for centuries."
Madrid may choose to strangle the independent movement slowly.
But Catalan separatists may have the resilience to see it through.
The stage is set for a titanic battle of wills, the future of a nation hanging in the balance.Let's