Offices were raided and members of the Catalan government arrested on September 20 by Spain's Guardia Civil police as part of an effort to derail an independence vote scheduled for October 1. Madrid ruled the referendum illegal and imposed a ban. Police seized ballots and documents related to the referendum and later took over the payment of essential services and public workers' salaries to prevent Catalonia from spending money. The Spanish government also ordered banks to control all movements in the accounts and credit cards managed by Catalan leaders.

On September 22, the Spanish Interior Ministry chartered three ferries to house police in preparation for a crackdown.

"Three ships arrived and will stay in the ports of Barcelona and Tarragona, where police and Guardia Civil forces will stay," said the central government's representative office in Catalonia.