That's absolutely wrong. And thinking that Spain will need to fire on civilians is ridiculous. Either wishful thinking or you are ridiculously misinformed.
The 2011 London riots were extremely severe and lasted three days, despite not really having any political basis or leadership, and there were plenty of rightwing politicians calling for military intervention.
What I think will happen? Apart from what they themselves will do, nothing. Public officers, including regional police, won't resist since their payroll depends on them obeying orders. Politicians might play some games but they know that a single death will trigger the rebellion prosecution and get them jailed for 30 years.
So it will most likely amount to some unrest, demostration, vandalism and all the noise we're used to.
All it takes is for armed police/military to meet large angry crowds that won't back down. If Spain sends the military to arrest the Catalonian government, we may end up with both of the ingredients. Perhaps a new Syria is unlikely, but is something on the scale of Euromaidan really that hard to imagine?
I know nothing of Maidan protests. Spain has nothing to do with Egypt, Turkey or Syria. If Spain was remotely similar, every separatist would be jailed and we wouldn't be having this conversation at all.
Why would Spain be immune to events like these while the people are easily as riled up as they were in Ukraine? Spain happens to have a history of civil war too.
This is terribly unfair. Worse. It's wrong. Not that our grandparents hadn't a civil war (they had) but the fact that this is any indication of environmental violence. Actually it's a disgusting unwarranted attack on an entire country.
All it takes is for armed police/military to meet large angry crowds that won't back down.
Police did meet angry crowds that won't back down last october 1st. There weren't shots or deads.
If Spain sends the military to arrest the Catalonian government, we may end up with both of the ingredients.
Spain would not send military to arrest someone. It would send police like any other regular country. If rogue regional police will shoot them, then we're not talking about an arrest, but about a full-blown armed rebellion. So please, stop spreading confusion.