Decades of internal political strife had followed the end of the Exarchate of Ravenna in 751 among various settlements vying for supremacy and between pro- and anti-Constantinopolitan factions; attempts by church authorities to acquire temporal influence have also been a factor.

A temporary shift of Venetian loyalties toward the Franks has resulted in somewhat permanent naval conflict in the Adriatic, only interrupted by a truce in 807–808.

The pro-Frankish faction had finally been able to seize power under Obelerio degli Antoneri in 804.

Obelerio and his brother Beato have brought Venice into the orbit of the Carolingian Empire.

However, by calling in Charles's son Pepin, rex Langobardorum, to his defense, Obelerio raises the ire of the populace against himself and his family and they are forced to flee during Pepin's siege of Venice.

The siege proves a costly Carolingian failure.

It lasts six months, with Pepin's army ravaged by the diseases of the local swamps and eventually forced to withdraw.

A few months later Pepin himself will die, apparently as a result of a disease contracted here.

A Turkish revival in the 1140s nullifies many of the Christian gains in Outremer, but greater damage is done to imperial security by dynastic strife in Constantinople, in which the largely French contingents of the Fourth Crusade and their Venetian allies intervene.

These crusaders in 1204 install Count Baldwin of Flanders in the capital as emperor of the so-called Latin Empire of Constantinople, dismembering the old realm into tributary states where West European feudal institutions are transplanted intact.

Independent Greek kingdoms are established, following the fall of Constantinople to the Latins, at Nicaea and Trebizond (present-day Trabzon) and in Epirus from remnant imperial provinces.

Turks ally with Greeks in Anatolia against the Latins, and Greeks with Turks against the Mongols.

The Serbs occupy parts of northern and eastern Albania toward the end of the twelfth century.

In 1204, after Western crusaders sack Constantinople, Venice wins nominal control over Albania and the Epirus region of northern Greece and takes possession of Durrës.

A prince from the overthrown imperial ruling family, Michael Komnenos, makes alliances with Albanian chiefs and drives the Venetians from lands that now make up southern Albania and northern Greece.

In 1204 he sets up an independent principality, the Despotate of Epirus, with Janina (now Ioannina in northwest Greece) as its capital.

Mainland Greece is split between the Greek Despotate of Epirus (a Byzantine successor state) and French rule (known as the Frankokratia), while some islands come under Venetian rule following the Fourth Crusade and the fall of Constantinople to the "Latins" in 1204.

Southwest Europe (1108 – 1251 CE): Iberian Reconquest and the Mediterranean Crown

Between 1108 and 1251 CE, Southwest Europe—stretching from the Pyrenees to Sicily and from the Atlantic to the Adriatic—entered an age of expansion and maritime integration.
The Crown of Aragon united Catalonia’s merchants with Iberia’s crusading frontier; Portugal secured its independence; Castile and León advanced across the Meseta; and Frederick II’s Sicily became the intellectual and administrative jewel of the Mediterranean.
Across these realms, irrigation, shipbuilding, and law combined to create the foundations of Europe’s first commercial empires.

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Geographic and Environmental Context

Southwest Europe joined the western Mediterranean with the Atlantic façade—a continuum of mountain valleys, river basins, and maritime corridors.

• Mediterranean sphere: Catalonia, Valencia, Murcia, Andalusia, Provence’s western marches, and the islands of the Balearics, Sardinia, and Sicily.

• Atlantic sphere: Portugal, Galicia, León, Castile, Navarre, and the Basque coast.

The Ebro, Guadalquivir, and Douro rivers served as inland arteries, while the Strait of Gibraltar linked the Atlantic to the Mediterranean.
This geography united irrigated gardens, vine terraces, and maritime forests into a single, resource-rich ecosystem that fueled both agrarian and naval growth.

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Climate and Environmental Shifts

The Medieval Warm Period provided stability, though droughts periodically stressed Iberian interiors.

• Irrigation in Valencia, Murcia, and Sicily countered dryness, sustaining year-round cultivation.

• Atlantic coasts remained temperate and wet, supporting fisheries and viticulture.

• Forests of the Cantabrian and Pyrenean ranges supplied timber for expanding shipyards.
  Regional diversity fostered complementary economies—cereals and sugar in the south, wine and wool in the north, and maritime exports along both coasts.

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Societies and Political Developments

Aragon and the Western Mediterranean:
The Crown of Aragon emerged in 1137 from the union of Aragon and Barcelona, forming a powerful maritime polity.
Its kings extended dominion over Catalonia, Roussillon, and by 1229–1235, the Balearic Islands; Valencia fell in 1238 after the decisive Christian victory at Las Navas de Tolosa (1212) broke Almohad strength.
Andorra remained under Catalan suzerainty.
Aragonese fleets reached Sardinia, while Barcelona became a hub of Mediterranean credit and commerce.

Portugal and the Atlantic Kingdoms:
Afonso I (r. 1139–1185) achieved independence from León, securing Lisbon (1147) and the Algarve by the 1240s.
Royal charters (for Lisbon, Coimbra, Porto) encouraged merchant autonomy and agricultural colonization.
Portugal’s stable frontiers and coastal wealth established it as Europe’s first enduring Atlantic monarchy.

Castile, León, and Navarre:
Alternating unions and separations between Castile and León defined 12th-century politics; kings Alfonso VII and Alfonso VIII expanded southward into Toledo and La Mancha.
Frontier towns like Madrid, Salamanca, and Burgos became centers of law and trade.
Navarre maintained independence as a Pyrenean crown; Basque valleys retained their fueros (local charters) and self-governing institutions.

The Almohads and al-Andalus:
The Almohad Caliphate replaced the Almoravids in the early 12th century, revitalizing Islamic scholarship and urban life in Seville, Córdoba, and Granada.
Despite Almohad reformism, internal divisions weakened resistance; after 1212, Muslim rule contracted to Granada, which survived as a tributary emirate.
Urban irrigation systems and craftsmanship in Andalusia and Valencia influenced Christian urban economies long after conquest.

Sicily and the Hohenstaufen Empire:
Under Frederick II (r. 1197–1250), Sicily became the Mediterranean’s most advanced polity.
From Palermo, the emperor codified law (the Constitutions of Melfi, 1231), founded universities, and patronized Arabic, Greek, and Latin scholarship.
Sardinia drew Aragonese interest, while Malta remained a Sicilian outpost controlling Mediterranean sea lanes.
Frederick’s court epitomized cultural fusion—where Muslim science, Latin administration, and Norman architecture met.

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Economy and Trade

Agrarian and Industrial Production:

• Irrigated estates (huertas) of Valencia, Murcia, and Sicily produced sugar, rice, citrus, and silk.

• Castile and León supplied wool and grain to northern markets.

• Portugal’s Minho and Douro valleys cultivated vineyards; fisheries at the Algarve and Galicia sustained Atlantic trade.

• Basque ironworks and shipyards produced anchors, nails, and ocean-ready hulls.

Trade and Commerce:

• Mediterranean: Venice, Genoa, and Pisa dominated Levantine routes, while Barcelona and Valencia expanded in western circuits.

• Atlantic: Lisbon, Porto, and Cantabrian ports traded wine, salt fish, and timber with England, Brittany, and Flanders.

• Sicily and Apulia exported grain and sugar to Italy; Andalusian ports exported textiles, fruit, and ceramics.
  Notarial contracts, maritime insurance, and public shipyards standardized economic exchange across the region.

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Belief and Symbolism

Christian–Islamic Convergence:
The frontier of Iberia was both battlefield and bridge.
Crusading ideology sanctified conquest, while Islamic architecture, science, and agriculture profoundly influenced Christian society.
Cathedral building in Toledo, Valencia, and Burgos echoed both Gothic and Moorish design.

Frederick II’s Rational Court:
In Palermo, Greek and Arabic scholars translated Aristotle and Euclid; falconry, astronomy, and law flourished under imperial patronage.
His court symbolized a Mediterranean humanism centuries ahead of its time.

Pilgrimage and Devotion:
The Camino de Santiago united Iberia’s kingdoms spiritually and commercially, sustaining Santiago de Compostela as a pan-European shrine.
Monastic orders—the Cistercians, Knights of Calatrava, and Orders of Santiago and Aviz—defended and colonized the frontiers.

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Subsistence and Technology

• Irrigation systems (qanats and acequias) revitalized agriculture in Aragon and al-Andalus.

• Hydraulic mills and riverine warehouses improved grain processing.

• Basque and Portuguese shipyards refined stern rudders and clinker hulls, precursors to oceanic vessels.

• Portolan charts and magnetic compasses circulated through Italian pilots.

• Architectural innovation: coral masonry in Sicily, ribbed vaulting in Iberia, and civic loggias in Aragonese ports.

Technology bound rural production to maritime ambition, transforming the peninsula into a laboratory of navigation and law.

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Movement and Interaction Corridors

• Mediterranean sea-lanes: Barcelona ⇄ Marseille ⇄ Genoa ⇄ Palermo ⇄ Alexandria.

• Atlantic routes: Lisbon ⇄ Bristol ⇄ Flanders ⇄ Bordeaux.

• Inland arteries: Ebro, Douro, and Guadalquivir rivers connecting highland farms to seaports.

• Pyrenean and Rhône passes: Catalonia and Provence’s gateways to France and Italy.

• Straits and narrows: Messina, Otranto, and Gibraltar—the gateways of empire.

These corridors bound the region into Europe’s dual maritime economy: Mediterranean and Atlantic.

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Adaptation and Resilience

• Irrigation and terrace farming stabilized food production under variable rainfall.

• Urban autonomy and municipal charters balanced royal power with local initiative.

• Maritime diversification (Atlantic and Mediterranean fleets) buffered commerce from political upheavals.

• Cross-cultural exchange—Muslim science, Christian law, and Jewish finance—enriched statecraft and learning.
  Resilience in this region stemmed from adaptability: an ability to absorb, reform, and synthesize across faiths, climates, and seas.

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Long-Term Significance

By 1251 CE, Southwest Europe had become Europe’s hinge between the Atlantic and the Mediterranean:

• Aragon anchored a western maritime empire; Barcelona and Valencia rose as centers of trade and law.

• Portugal emerged as an independent Atlantic kingdom with enduring stability.

• Castile and León consolidated the Meseta, preparing for Andalusian conquest.

• Sicily, under Frederick II, stood as a beacon of learning and centralization.

• Venice and Genoa extended their reach into Iberian and Maghrebi waters.

Here, the fusion of Islamic irrigation, Latin legalism, and nautical science forged the intellectual and technological foundations for Europe’s coming age of exploration.

Mediterranean Southwest Europe (1108 – 1251 CE): Almohads, Aragon’s Union, and Hohenstaufen Sicily

Climate and Environmental Shifts

• Productive regimes persisted with localized dryness in Iberia; irrigation buffered Valencia, Murcia, Andalusia, Sicily.

Societies and Political Developments

• Crown of Aragon (union 1137 of Aragon and Barcelona) expanded into Catalonia, Roussillon, and the Balearics’ approaches; Andorra remained within Catalan orbit.

• Almohads superseded Almoravids in al-Andalus; Christian advances paused until Las Navas de Tolosa (1212) opened the Guadalquivir. Valencia (1238) and the Balearics (1229–1235) fell to King James I.

• Portugal consolidated Algarve and Alentejo frontiers; Castile/León held Toledo and pushed La Mancha; Madrid grew as a frontier town.

• Hohenstaufen Sicily under Frederick II (r. 1197–1250) centralized law and science; Sardinia drew Aragonese interest; Venice led Adriatic power and eastern ventures.

• Malta attached to the Sicilian crown.

Economy and Trade

• Venice, Genoa, Pisa dominated Levantine–western circuits; Barcelona–Valencia fleets grew in western routes.

• Sicily/Apulia exported grain, sugar, and citrus; Andalusia/Valencia irrigated gardens sustained urban markets; Algarve fisheries and salt fed Atlantic–Mediterranean trade.

Subsistence and Technology

• Hydraulic estates in al-Andalus and Sicily; notarial–credit instruments in Italian and Catalan cities; communal shipyards standardized galleys.

Movement and Interaction Corridors

• Rhône–Ligurian pivot into Genoa and Venice; Ebro–Pyrenees to Barcelona; Guadalquivir/Segura/Turiariver basins supplied Seville–Valencia ports; Strait of Messina and Otranto gates for Sicilian–Italian flows.

Belief and Symbolism

• Almohad reformism; Latin cathedral building—Burgos (nearby, outside core) influenced Toledo, Valencia; Frederick II’s court culture blended Arabic–Latin–Greek learning; crusading mobilizations flowed through Italian/Iberian ports.

Long-Term Significance

By 1251, Aragon anchored a western thalassocracy; Venice led the Adriatic; Frederick II’s Sicily structured the central Med; Iberia’s Christian kingdoms were poised for decisive 13th-century gains.

Roger II of Sicily dies at Palermo on February 26, 1154 and is buried in the Cathedral of Palermo.

He is succeeded by his fourth son, William, who had grown up with little expectation of ruling.

The deaths of his three older brothers Roger, Tancred, and Alfonso between 1138 and 1148 had changed matters, though when his father dies William is still not well-prepared to take his place.

On assuming power, William keeps the administration that had guided his father's rule for his final years.

Only the Englishman Thomas Brun is removed, and the chancellor Maio of Bari is promoted.

The real power in the kingdom is at first exercised by Maio, a man of low birth, whose title ammiratus ammiratorum is the highest in the realm.

Maio continues Roger's policy of excluding the nobles from the administration, and seeks also to curtail the liberties of the towns.

The barons, always chafing against the royal power, are encouraged to revolt by Pope Adrian IV, whose recognition William has not yet sought, by the East Roman Emperor Manuel I Komnenos, and by the Holy Roman Emperor Frederick I, who had had canceled his plan to invade Sicily when Roger died.

Continuing his father’s ambitions, William offers peace to Manuel, is refused, and then makes peace with Venice, thus depriving Constantinople of a war fleet.

Manuel sends a fleet to attack Ancona in 1155, capturing much of the region of Apulia, but it is too late for a revival of Greek imperialism in the West; under William’s command, a joint opposition force of Germans, Venetians, and Normans gathers to oppose the invasion.

Making contact with local rebels who were hostile to the Sicilian crown, imperial forces quickly overrun the coastlands and began striking inland.

Pope Adrian IV watches these developments with some satisfaction.

The Papacy has never been on good terms with the Normans of Sicily, except when under duress by the threat of direct military action.

Having the "civilized" Eastern Roman Empire on its southern border is infinitely preferable to Adrian than having to constantly deal with the troublesome Normans.

Therefore, negotiations are hurriedly carried out, and an alliance is formed between Adrian and Manuel.

Adrian undertakes to raise a body of mercenary troops from Campania.

Meanwhile, Manuel dreams of restoration of the Roman Empire; this is, however, at the cost of a potential union between the Orthodox and the Catholic Church.

Negotiations for union of the eastern and western churches, which had been in a state of schism since 1054, soon get underway.

The combined Papal-Imperial forces join with the rebels against the Normans in southern Italy, achieving a string of rapid successes as a number of cities yield either to the threat of force or to the lure of gold.

The future looks bleak for the Sicilians.

A rebellion has broken out against William I of Sicily, and the forces of Constantinople, encouraged by Pope Adrian IV, invades Apulia.

At Brindisi in 1156, the joint force of Germans, Venetians, and Normans loyal to William defeats the invading army dispatched by Emperor Manuel I Komnenos, ending Constantinople’s influence in Italy.

William crushes the rebellion and …