This occupation of the Iberian peninsula fueled local nationalism, and soon the Spanish and Portuguese fought the French using guerilla tactics, defeating the French forces at the Battle of Bailén (June and July 1808). Britain sent a short-lived ground support force to Portugal, and French forces evacuated Portugal as defined in the Convention of Sintra following the Allied victory at Vimeiro (21 August 1808). France only controlled Catalonia and Navarre and could have been definitely expelled from the Iberian peninsula had the Spanish armies attacked again, but the Spanish did not.