Playing as Spain, I once had a major problem with them. My fleets were all out beating up on Pirates, protecting trade fleets and them the BPs blockaded my only trade port in Spain -- Cartagena -- with 12 galleys, cutting off 100% of my trade income. It took me several turns together to get a fleet together to deal with the 12 galleys, during which time I realized to have your tax income cover your upkeep...