Nothing is more difficult for the Spanish government to stomach than the ongoing independence ambitions in Catalonia. It’s not hard to see why: Catalonia has been part of Spain for centuries, and is one of the nation’s wealthiest regions. This has meant the government aggressively trying to tamp down secessionist sentiments.

Today, that’s meant threatening to arrest 712 Catalan mayors who have agreed to allow the use of public space for the referendum. The public prosecutor summoned all of those mayors, threatening to arrest them if they didn’t show up for their public warning, or if they allowed the vote.

The mayors are describing this as an unprecedented move, and indeed, there are only 948 mayors total, so this is a threat to jail a heavy majority of them. Still, the secession movement is likely to endure either way.

Modern Catalonian nationalism has its origin in a 19th century revisiting of their historic culture and language. The region had traditionally had substantial autonomy within Spain, which was revoked during the Spanish Civil War.

Autonomy was to be re-granted in 1979 as part of a new constitution, and reduced the push for secession for decades. It was after a 2010 court ruling that a revised clause of autonomy was unconstitutional that many again began to see autonomy as unsustainable, and secession as the long-term answer.