This decision by Napier was the deciding factor in the outcome of the battle, and the Miguelite crews proved no match for the Liberal crews, most of them being former Royal Navy personnel that had been discharged and sought service under Pedro I of Brazil. The battle resulted in four Miguelite ships of the line, one frigate and one corvette being captured, and the remainder of the Miguelite fleet retreating from the engagement. The action took place in context of the Liberal Wars, a Portuguese civil war fought between the King of Portugal, Dom Pedro, and a pretender named Don Miguel, whose supporters were called Miguelites. The battle had a decisive effect on the war, since the Miguelite fleet at Cape St. Vincent was the last significant naval force that Don Miguel could muster, his other naval forces being lost in the Battle of the Tagus on 11 July 1831 against a French fleet led by Albin Roussin. The Miguelite-held Lisbon, deprived of any chance to be resupplied via the sea, quickly capitulated.