Porto has a long tradition of defense of civil rights, for that reason is known as a liberal and progressive city. During 1832 and 1833 the population of this city withstood a long military siege by the royalist forces. The victory of the liberal cause was partly due to the sacrifice of its people, who fought to support the Constitutional Chart. As a result of this heroic action, King Pedro IV described it as the "very noble, undefeated and ever loyal" city of Porto.