Lisbon — Roman Olisipo, Muslim al-Ushbuna, Portuguese Lisboa — commands the estuary of the Tagus, the finest harbour of Atlantic Iberia. Conquered by Afonso Henriques and a Second Crusade fleet after the seventeen-week siege of 1147, it grew from frontier prize into the effective capital of Portugal: seat of the court from the mid-thirteenth century, its greatest port, and by the end of the Middle Ages one of the Atlantic world's great cities.
Lisbon — Roman Olisipo, Muslim al-Ushbuna, Portuguese Lisboa — commands the estuary of the Tagus, the finest harbour of Atlantic Iberia. Conquered by Afonso Henriques and a Second Crusade fleet after the seventeen-week siege of 1147, it grew from frontier prize into the effective capital of Portugal: seat of the court from the mid-thirteenth century, its greatest port, and by the end of the Middle Ages one of the Atlantic world's great cities.
Its medieval story is the kingdom's in miniature: mosque made cathedral in 1147; an English crusader as first bishop; royal charters and Italian merchants building the river trade; the university founded by King Denis in 1290; the crisis of 1383–1385 in which Lisbon's citizens made João of Aviz king; and the Tagus waterfront from which, at the period's very edge, the ocean routes opened.
Under Muslim rule from the eighth century, Lisbon was the north-westernmost great city of al-Andalus: a walled port on the castle hill above the Tagus, described by the 1147 eyewitness as teeming with refugees from the fallen frontier towns, its wealth in orchards, fisheries, and the river trade. It had been raided before — Alfonso VI held it briefly after 1093 — but held its hinterland until the kingdom of Portugal closed in.
The siege of 1147 — Afonso Henriques's army joined by the storm-diverted crusader fleet from England, Flanders, and the Rhineland — ended on 24 October with the city's surrender. The great mosque became the cathedral (the Sé's Romanesque core still stands), Gilbert of Hastings became bishop, crusader settlers took houses and liberties, and the Muslim and Mozarabic population passed under Portuguese rule, the former concentrated in the Mouraria quarter that kept the name into modern times.
Lisbon's rise to capital was commercial before it was constitutional. The Tagus anchorage made it the hinge between Mediterranean and northern sea-lanes; Genoese and Placentine merchants appear in royal grants from the thirteenth century, and King Denis (1279–1325) — who founded the university at Lisbon in 1290, chartered fairs, planted the pine forests for shipbuilding, and hired the Genoese Manuel Pessanha as hereditary admiral in 1317 — built the crown's maritime policy on the city's waterfront. The court settled definitively at Lisbon under Afonso III after 1255.
The city's political weight showed in the kingdom's great crisis: in 1383–1385 Lisbon's merchants and craft guilds were the engine of the revolution that made the Master of Aviz king João I — the city withstood a Castilian siege through the plague summer of 1384, and its money and militia underwrote the victory at Aljubarrota. The Aviz monarchy repaid it: Lisbon's cortes, its customs house, and its arsenal became the kingdom's financial core, and by 1500 the city that the Middle Ages had made was the staging port of a world empire.
Medieval Lisbon climbed from the river in tiers: the castle of São Jorge on the summit; the Alfama and Mouraria quarters on the slopes — fishermen, Muslims under protection, later the judiaria of one of Iberia's major Jewish communities; the cathedral and merchant town along the shore; and the Rossio commons where the fairs and, in 1383, the revolution assembled. Earthquakes (1344, 1356) and plague repeatedly scarred it; royal building — Denis's wall, Ferdinand I's great enceinte of the 1370s, thrown up in haste against Castile — repeatedly enlarged it.
Its tongues and trades were a port's: Portuguese, Arabic, Hebrew, Genoese, and the English and Flemish of the wine and salt fleets. The city's liberties — confirmed and contested in charter after charter — made its concelho a political actor kings had to bargain with, never more decisively than when it chose its own king in 1383.