These new Mossos were a militarized corps having little similarity to the earlier incarnations, with limited powers and small numbers, which was in charge of protecting the government buildings of the Province of Barcelona.

It was created as a complement to the regular troops of the Bourbon army, which opposed the Miquelets, who survived as rebel supporters of Archduke Charles.

It was eventually placed under military jurisdiction, but was less centralised than the Spanish police force (then known as the Intendencia General de Policía) formed in 1817, or the yet-to-be-established Guardia Civil.

After the Spanish Civil War, the last Mossos left Catalonia with the President of the Generalitat, and the corps was dissolved by the Francoist authorities.

The Mossos keep some officers in Catalonia to support anti-terrorism operations, handle identity documents, police immigration, and execute other limited responsibilities of the central government.

Another rationale for its creation was to transfer responsibility for prisons to the Generalitat de Catalonia; this was felt to require a protocol to deal with riots or hostage-taking.