The capture of the city of Lisbon from the Almoravid Muslims in October 1147 after a months-long siege was a by-product of the Second Crusade to the Holy Land and the only major Christian victory of that campaign. It proved to be a pivotal turning point in the history of Portugal as it mutated from being a subordinate vassal of León into an independent Christian kingdom.
When he announced the start of the Second Crusade, Pope Eugene III, echoing an earlier mandate from Pope Urban II, stated that Christians in the Iberian Peninsula could crusade against the Muslims there rather than travel to the Holy Land. On June 16, 1147, 164 ships carrying 6,000 English and Scottish, 5,000 German, and 2,000 Flemish crusaders put in to Porto to escape a storm. Afonso Henriques, self-proclaimed King of Portugal, asked them to join his own personal crusade to capture Lisbon from the Muslims. He offered them the moveable goods of the Muslims in the city and any ransoms that could be extracted.
The crusaders agreed and, on July 1, 1147, laid siege to Lisbon, while Afonso and his army occupied the surrounding countryside. The crusaders built mangonels and other devices and bombarded the city. The Muslims launched a sortie and burned the siege engines. Thereafter the fighting almost stopped as the crusaders settled down to a blockade, finally broken when the crusaders captured a section of the city wall. On October 21, the garrison agreed to surrender on condition they were allowed to march out freely. The gates of Lisbon were opened four days later, which brought the siege to an end on October 25, 1147.
Although the terms of surrender included safe passage of Lisbon’s inhabitants after they relinquished a portion of their wealth, the foreign crusaders sacked the city and, according to a contemporary chronicle, took an unknown number of lives before being called off. Many English crusaders opted to stay in Portugal—one of them became Bishop of Lisbon—while the Germans and Flemings continued to the Holy Land. Lisbon became capital of Portugal, which won papal recognition as an independent kingdom.
The siege of Lisbon is considered the only true victory of the Second Crusade, which was otherwise a humiliating failure.
Losses: Crusader, minimal of 15,000; Muslim, few of 7,000-strong garrison; civilian, unknown.