Southwest Europe (1252 – 1395 CE): Mediterranean Thalassocracies and the Atlantic Turn

From the lagoons of Venice to the harbors of Lisbon, the southwest rim of Europe entered the Late Middle Ages as one of the world’s most dynamic maritime zones. The period between 1252 and 1395 witnessed the zenith of the Crown of Aragon’s thalassocracy, the consolidation of Castile and Portugal, and the financial and naval dominance of the Italian city-republics. Across the Mediterranean and Atlantic, fleets, fairs, and fortresses bound Europe’s southern peninsulas into an interlinked economy whose rhythms were set by wind, grain, and gold.

Geography and Climate

The subregion encompassed the Iberian Peninsula, the Italian peninsula and islands, and the surrounding seas—from the Guadalquivir and Tagus basins to the Venetian Adriatic and the Tyrrhenian and Balearic waters.
The onset of the Little Ice Age after 1300 brought cooler, wetter variability: Andalusian and Sicilian irrigation maintained productivity, while drier cycles in La Mancha and Alentejo encouraged sheep and transhumant herding. Maritime provisioning stabilized populations through famine years, even as the Black Death (1348–1352) devastated the great ports—Barcelona, Valencia, Genoa, Venice, and Naples—with partial demographic recovery by the century’s end.

Mediterranean Crowns and City-Republics

The Crown of Aragon, forged by the thirteenth-century conquests of James I, reached its maritime zenith. Catalan and Valencian fleets dominated the western Mediterranean; Sardinia was taken in the 1320s, and Sicily, freed from Angevin control after the Sicilian Vespers (1282), entered Aragon’s orbit. Barcelona’s merchants financed convoys to Tunis, Alexandria, and Constantinople, while Majorcan cartographers drew the most precise sea charts of the age.

To the west, Castile completed the reconquest of Andalusia, leaving Granada as the last Muslim emirate. The Guadalquivir valley’s cereals and Seville’s shipyards enriched the Castilian crown, while Madrid and La Mancha evolved into the agrarian-sheep core of the realm. Portugal, meanwhile, under Afonso III and Dinis I, stabilized its southern frontier in the Algarve and built the maritime forests of Leiria for ship timber. After dynastic crisis (1383–1385), João I’s victory at Aljubarrota and the Treaty of Windsor (1386) with England secured independence and inaugurated the Anglo-Portuguese alliance that would anchor the next century’s explorations.

Across the sea, Italy’s mercantile powers contested every horizon. Venice, from its lagoon capital, extended a maritime empire through the Adriatic and Aegean; its Arsenal mass-produced galleys and its patriciate ruled an empire of grain and spice. Genoa, facing west, financed expeditions and monopolized Tyrrhenian trade from Corsica to Tunis. In Florence, textile wealth and banking consolidated under the merchant guilds, while the Angevin kingdom of Naples and the Aragonese Sicily contended for southern Italy. Malta, Sardinia, and the Balearics served as naval stepping-stones, their harbors echoing with the languages of sailors from every sea.

Economy and Trade

Southwest Europe functioned as a dual maritime engine—Aragonese–Italian in the Mediterranean and Castilian–Portuguese in the Atlantic.

• Mediterranean circuits: Venetian and Genoese fleets carried Levantine spices, silks, and sugar; in return, they exported grain from Sicily and Apulia, wine and oil from Iberia, and salt from Ibiza and Trapani.

• Western basins: Barcelona, Valencia, and Majorca knit the western Mediterranean to Atlantic routes through Gibraltar.

• Atlantic façade: Castilian and Portuguese merchants exported wool, iron, wine, and salted fish; Castile’s Mesta(chartered 1273) organized transhumant flocks whose wool fed Flemish and Italian looms. Basque forgessupplied anchors, nails, and artillery; shipyards at Bilbao, Lisbon, and Porto produced cogs and caravels.

• Banking and cartography: Genoese and Venetian financiers underwrote commerce, while Catalan and Majorcan mapmakers synthesized Mediterranean and Atlantic knowledge into the new portolan charts.

Mixed agriculture—grains, vines, olives—and irrigation in the Valencia and Murcia huertas sustained populations; the Algarve, Sicily, and Crete pioneered sugar cultivation, a foretaste of the colonial plantations to come.

Movement and Interaction Corridors

Sea routes defined the region’s geography.
The Strait of Gibraltar linked Lisbon, Seville, and Barcelona to Tunis and Alexandria; the Messina and Otranto Straits funneled Sicilian and Adriatic convoys; the Venetian–Aegean corridor joined Constantinople to the Po valley.
Overland arteries—Ebro–Pyrenees, Tagus–Guadiana, Po–Alps—fed the ports, while the Douro road connected the Castilian plateau to Porto’s wine markets. The pilgrim routes to Santiago de Compostela continued to channel people and goods across northern Iberia, even amid war and plague.

Belief and Symbolism

Faith framed identity in a region of plural crowns.
The mendicant orders—Franciscans and Dominicans—flourished in Barcelona, Valencia, Venice, and Naples, preaching reform and mercy during plague years.
Cathedrals such as Seville’s, Valencia’s, and Florence’s Duomo, and civic loggias in Italian and Catalan cities expressed both religious devotion and urban pride.
The lingering influence of the Avignon Papacy tied Provençal, Aragonese, and Italian politics to papal diplomacy, while the Reconquista and frontier crusades gave Iberian warfare a sanctified rhetoric that foreshadowed later overseas expansion.

Adaptation and Resilience

Despite climatic uncertainty and epidemic loss, Southwest Europe remained remarkably adaptive.

• Irrigation, terrace agriculture, and maritime provisioning cushioned drought.

• Polycentric power—Venice, Genoa, Aragon, Castile, Portugal—allowed commerce to shift ports and flags as crises arose.

• Guild statutes and municipal charters stabilized labor and credit after the Black Death.

• The recovery of the 1380s–1390s re-energized trade, strengthened dynasties, and renewed shipbuilding, positioning the region for its fifteenth-century ascent.

Long-Term Significance

By 1395 CE, Southwest Europe stood as the beating heart of the late-medieval maritime world.
In the Mediterranean, Venice ruled the Adriatic lanes, Genoa and Florence financed the wider economy, and Aragon’s Catalan fleets mastered the western sea.
Across the Iberian Peninsula, Castile and Portugal unified their realms and turned outward to the Atlantic, where Lisbon’s and Bilbao’s shipwrights were already experimenting with ocean-going hulls.
From the Rialto to Lisbon, from Barcelona to Seville, merchants, mapmakers, and mariners laid the logistical and intellectual foundations of Europe’s global age.
The dual maritime systems of the Mediterranean thalassocracies and the Atlantic wool-iron networks formed a single economic engine—one that would propel Iberia and Italy beyond their seas and into the wider world of the fifteenth century.

Mediterranean Southwest Europe (1252 – 1395 CE): Aragonese Thalassocracy, Venetian Hegemony, and Castilian–Portuguese Consolidation

Geographic and Environmental Context

Mediterranean Southwest Europe includes Portugal’s Algarve and Alentejo, Spain’s Extremadura, Andalusia, Murcia, Valencia, Castile/La Mancha, southeastern Castile and León, Madrid, southeastern Rioja, southeastern Navarra, Aragon, Catalonia, the Balearic Islands, Andorra, and all of Italy (peninsula, Sicily, Sardinia, Venice), plus Malta.

• Anchors: the Guadalquivir Valley (Seville–Granada frontier), the Tagus–Alentejo/Algarve under Portugal, Madrid–La Mancha–Extremadura consolidated in Castile, the Valencia/Murcia huertas, the Ebro–Barcelona–Aragon–Andorra corridor, the Balearics under Aragon, Venice as Adriatic hegemon, Genoa and Florence as rivals in Liguria and Tuscany, the Kingdom of Naples/Angevin South, Sicily in Aragonese orbit, Sardinia, and Malta as naval outposts.

Climate and Environmental Shifts

• Little Ice Age onset (~1300) brought cooler, wetter variability; irrigation kept Valencia, Murcia, Andalusia, Sicily productive.

• Black Death (1348–1352) devastated Barcelona, Valencia, Genoa, Venice, Naples, with partial demographic recovery by the 1390s.

Societies and Political Developments

• Crown of Aragon: James I’s conquests of Valencia (1238) and Balearics (1229–35) were integrated; Sardinia conquered (from 1320s); Sicily entered Aragonese orbit after the Sicilian Vespers (1282); Catalonia projected power across the western Med.

• Castile consolidated Andalusia; Granada survived as the last Nasrid emirate; Madrid matured under Castilian administration; La Mancha became a grain–sheep heartland.

• Portugal stabilized Alentejo/Algarve and built Atlantic–Med linkages.

• Italy: Venice dominated Adriatic–Aegean routes; Genoa contested Tyrrhenian and western lanes; the Angevin Kingdom of Naples and Aragonese Sicily rivaled in the south; Sardinia held by Aragon; Malta under Sicilian–Aragonese control.

• Andorra remained a Pyrenean co-principality (Counts of Foix/Bishop of Urgell).

Economy and Trade

• Venetian hegemony in the Adriatic–Aegean; Genoese finance and Ligurian shipping; Barcelona–Valencia–Majorca fleets knit the western basin.

• Exports: grain (Sicily/Apulia), olive oil/wine (Iberia/Italy), sugar/citrus (Sicily/Valencia), salt (Ibiza, Trapani);

• Imports: spices/silks via Levant; wool from La Mancha and Aragon fed Italian and Catalan looms.

• Banking: Venetian and Genoese firms, Catalan–Majorcan cartography and credit.

Subsistence and Technology

• Canal estates and huertas in Valencia/Murcia/Andalusia; Venetian Arsenal mass-produced galleys; Rialto and Piazza San Marco symbolized mercantile power.

Movement and Interaction Corridors

• Strait of Gibraltar linked Atlantic–Med flows; Messina straits managed Sicily transit; Po–Venetian lagoon fed Adriatic convoys; Ebro–Pyrenees, Tajo–Guadiana corridors fed Iberian ports.

Belief and Symbolism

• Avignon Papacy (outside region yet influential) shaped Provençal–Italian–Aragonese politics;

• Mendicant orders (Franciscans, Dominicans) in Barcelona, Valencia, Venice, Naples;

• Cathedrals and civic loggias embodied urban identities.

Adaptation and Resilience

• Irrigation + maritime redundancy cushioned climatic stress;

• Plural city-republics and crowns allowed merchants to shift flags, ports, and credit;

• Guilds and statutes stabilized labor and prices post-plague.

Long-Term Significance

By 1395, Mediterranean Southwest Europe was a dual maritime engine—Venice in the east, Crown of Aragon in the west—nested with Castile–Portugal consolidation on land. The subregion underwrote the late-medieval Mediterranean economy, setting the stage for 15th-century imperial and commercial expansion.

Atlantic Southwest Europe (1252 – 1395 CE): Wool, Iron, Wine, and the Atlantic Turn

Geographic and Environmental Context

Atlantic Southwest Europe includes Portugal’s Lisbon, Beira, Minho, Trás-os-Montes, and Spain’s Galicia, Asturias, Cantabria, Basque Country, Castile and León, northern Rioja, and northern Navarra.

• Anchors: the Cantabrian coast (A Coruña–Gijón–Santander–Bilbao–San Sebastián), the Douro/Minho estuaries, and the Meseta–Cantabrian passes binding the plateau to Atlantic ports.

Climate and Environmental Shifts

• Little Ice Age onset (~1300) brought cooler, wetter weather; stormier Bay of Biscay; good fisheries persisted.

• Black Death (1348–1352) hit towns hard; ports recovered quickest via maritime trade.

Societies and Political Developments

• Castile and León unified under Alfonso X (r. 1252–1284), then fractured and reconsolidated amid the Trastámara coup (Pedro I vs Enrique II, 1366–1369).

• Portugal strengthened under Afonso III and Dinis (reforestation of Leiria for ship timber; University of Coimbra 1290), then defended independence in the Crisis of 1383–1385; João I and Aljubarrota (1385) sealed the Anglo-Portuguese alliance (Treaty of Windsor, 1386).

• Navarre navigated between France and Castile; Basque towns (Bilbao, charter 1300; San Sebastián) grew as maritime communes.

Economy and Trade

• Wool complex: Castilian wool—organized by the Mesta (founded 1273)—flowed through Burgos, León, and Cantabrian ports to Flanders and England.

• Basque iron & shipbuilding: forges supplied anchors, nails, artillery shot; yards built cogs and naos for Atlantic service and whaling.

• Wine & salt fish: Douro/Minho wines, Galician/Portuguese salt fish (cod, sardine) and tuna moved north; Lisbon/Porto emerged as major entrepôts.

• Finance & law: municipal fueros, urban consulates, and English–Portuguese treaties stabilized credit, convoys, and tariffs.

Subsistence and Technology

• Mixed Atlantic polyculture (rye/wheat, vines, chestnuts, cattle); stern-rudder hulls, improved rigging, magnetic compass and portolan practice diffused into Iberian waters.

Movement and Interaction Corridors

• Sea: Lisbon ⇄ London/Bristol; Cantabria ⇄ Flanders; Galicia ⇄ Brittany; pilgrim sailings to Santiago.

• Land: Meseta passes fed Burgos, León, Salamanca; Douro road/river linked Castile to Porto.

Belief and Symbolism

• Cathedrals and monasteries in Santiago, León, Burgos, Salamanca; confraternities of sailors and merchants venerating St. James and St. Nicholas kept social cohesion in plague decades.

Adaptation and Resilience

• Route redundancy (many ports, multiple passes), portfolio exports (wool–iron–wine–fish–salt), and crown–town compacts hedged risk from war, weather, and plague.

Long-Term Significance

By 1395, the Atlantic façade from Lisbon to San Sebastián had become a maritime-industrial platform: wool, iron, wine, and shipbuilding—backed by Portugal’s English alliance—set the stage for the 15th-century Atlantic turn and overseas exploration.

Mediterranean Southwest Europe (1384–1395 CE): Iberian Political Realignments, Genoese-Venetian Rivalries, and Cultural Continuities

The era 1384–1395 CE in Mediterranean Southwest Europe is marked by significant political shifts within Iberia, ongoing hostilities between maritime republics Venice and Genoa, and sustained cultural and intellectual activities despite political instability.

Iberian Political Realignments: Portugal and Castile

This period witnesses significant shifts on the Iberian Peninsula, notably through the political crisis following the death of King Ferdinand I of Portugal in 1383. This event precipitates the 1383–1385 Crisis in Portugal, leading to conflict with Castile. John I of Portugal (João I), supported by English forces, secures his throne at the decisive Battle of Aljubarrota (1385), ending Castilian ambitions to dominate Portugal and establishing the House of Aviz. This victory realigns regional power balances, reinforcing Portuguese independence and fostering a lasting alliance with England.

Renewed Genoese-Venetian Rivalries

The ongoing rivalry between maritime powers Venice and Genoa continues with intense naval confrontations and territorial contests in the Mediterranean. Their competition influences trade routes, commercial dynamics, and regional alliances, maintaining economic vitality despite intermittent warfare.

Cultural and Artistic Continuities

The region remains culturally vibrant. Artistic patronage continues to flourish in Italian city-states such as Florence, Venice, and Siena. Gothic architecture and painting maintain prominence, supported by prosperous urban communities that invest significantly in public works and artistic commissions.

Intellectual Advancements

Scholarly and literary endeavors persist amid political turmoil. The humanist movement gains momentum, with scholars revisiting classical texts and promoting a revival of ancient philosophies and literary forms. The literary and intellectual legacy of earlier figures like Petrarch and Boccaccio continues to influence contemporary thought and writing.

Legacy of the Era

The era 1384–1395 CE significantly shapes Mediterranean Southwest Europe through critical political realignments in Iberia, sustained maritime rivalries, and continuous cultural and intellectual productivity. These developments collectively enhance regional stability, reshape political dynamics, and sustain cultural resilience, leaving lasting impacts on subsequent historical trajectories.

Atlantic Southwest Europe (1384–1395 CE): Portuguese Independence Restored, Castilian Stability, and Navarrese Diplomatic Pragmatism

Between 1384 and 1395 CE, Atlantic Southwest Europe—including Galicia, northern and central Portugal, Asturias, Cantabria, and northern Spain south of the Franco-Spanish border (43.05548° N, 1.22924° W)—experienced profound political shifts, marked by Portugal’s decisive restoration of independence, continued stability in Castile, and cautious diplomacy in Navarre. Portugal emerged from a severe dynastic crisis with the establishment of the House of Aviz, securing sovereignty under King John I of Portugal (1385–1433 CE). Castile, under King John I (1379–1390 CE)and later his son Henry III (1390–1406 CE), maintained political stability and reinforced regional coherence. Navarre, under King Charles II "the Bad" (1349–1387 CE) and subsequently his son Charles III "the Noble" (1387–1425 CE), skillfully navigated complex Iberian alliances to preserve territorial integrity and regional autonomy.

Political and Military Developments

Portuguese Restoration of Independence and the Rise of the House of Aviz

Portugal faced a decisive turning point following the death of King Ferdinand I in 1383, sparking the 1383–1385 Crisis and war of succession. Led by John of Aviz, Portuguese forces decisively defeated Castilian claimants at the Battle of Aljubarrota (1385 CE), restoring Portugal’s independence. John was proclaimed King John I of Portugal, firmly establishing the Aviz dynasty. His strong leadership stabilized governance, unified civic identity, and reinforced Portuguese national sovereignty.

Castilian Stability and Governance under John I and Henry III

Castile maintained robust governance stability and administrative coherence under King John I, despite his failed attempt to incorporate Portugal. After John’s death in 1390, his son, Henry III "the Sufferer", decisively preserved Castilian internal stability, territorial integrity, and regional coherence. Henry III’s governance significantly solidified the Trastámara dynasty’s authority, laying foundations for future Castilian prosperity.

Navarrese Diplomatic Pragmatism under Charles II and Charles III

Navarre skillfully managed the transition from Charles II "the Bad" to his son, Charles III "the Noble" in 1387. Charles III decisively shifted Navarre’s diplomacy from opportunistic to pragmatic, fostering stability through improved relations with neighboring Castile, Aragón, and France. His careful diplomacy significantly preserved Navarre’s territorial integrity, regional autonomy, and internal stability.

Economic Developments

Agricultural and Economic Revitalization

The region sustained steady agricultural recovery, significantly benefiting from stable governance and restored political confidence. Improved agricultural practices (grains, olives, vineyards, citrus fruits, almonds), livestock husbandry, artisanal crafts, and consistent mining operations (gold and silver from Galicia and Asturias) reinforced economic resilience and growth.

Renewed Maritime Commerce and Trade Expansion

Portuguese ports (Lisbon, Porto, Braga, Coimbra) expanded significantly, reinforcing vibrant maritime commerce and international trade, particularly with northern Europe (England, Flanders, Normandy, Brittany). Galicia, notably A Coruña, likewise sustained active maritime trade, reinforcing regional economic stability and prosperity.

Pilgrimage Revival and Economic Continuity

Pilgrimage to Santiago de Compostela recovered fully, decisively bolstering the Galician economy through hospitality industries, trade, artisanal commerce, and infrastructure development. Renewed pilgrimage activity significantly reinforced Galicia’s economic vitality, cultural prominence, and regional identity.

Cultural and Religious Developments

Portuguese Cultural Renaissance under the Aviz Dynasty

Under King John I, Portugal decisively revitalized its cultural identity, intellectual traditions, and educational patronage. The establishment of stable governance allowed renewed support for literature, scholarly institutions, and royal patronage of arts and culture, shaping Portuguese linguistic standardization and cultural identity profoundly.

Galician Cultural Continuity and Ecclesiastical Patronage

Galicia maintained vibrant cultural resilience, decisively supported by ecclesiastical patronage and the economic revival linked to Santiago de Compostela’s pilgrimage activity. Scholarly initiatives, manuscript preservation, and significant architectural projects continued, reinforcing Galician cultural identity and international recognition.

Monastic Intellectual Influence and Ecclesiastical Authority

Monastic communities decisively contributed to scholarly activities, manuscript preservation, agricultural innovations, and educational reforms. Ecclesiastical authorities maintained significant influence over Iberian religious identity, social cohesion, and cultural resilience.

Persistent Cultural Syncretism and Local Traditions

Orthodox Christianity continued to integrate indigenous Iberian and Celtic traditions, especially in rural Galicia and northern Portugal. This cultural syncretism significantly reinforced regional identities, social cohesion, and cultural resilience during a transformative era.

Civic Identity and Governance

Portuguese Civic Unity and Governance Stability

The establishment of the Aviz dynasty under King John I decisively restored Portuguese civic unity, governance stability, and national identity following the succession crisis. Effective administration significantly solidified Portuguese national sovereignty and internal coherence.

Castilian Governance Stability and Territorial Integrity

Under John I and Henry III, Castile maintained robust governance stability, territorial integrity, and strengthened regional identity. Their effective leadership significantly reinforced Castilian civic cohesion and geopolitical stability.

Navarrese Regional Autonomy and Diplomatic Stability

Under Charles II and Charles III, Navarre carefully preserved regional autonomy, diplomatic neutrality, and governance stability. Effective diplomatic pragmatism significantly preserved territorial integrity, internal stability, and northern Iberian geopolitical coherence.

Notable Regional Groups and Settlements

• Portuguese: Successfully restored independence, decisively unified civic identity, and reinforced governance stability under King John I of the House of Aviz, significantly shaping Portugal’s enduring medieval trajectory.

• Castilians: Achieved decisive governance stability, territorial integrity, and reinforced regional identity under the Trastámara dynasty (John I and Henry III), significantly influencing Iberian geopolitical stability.

• Galicians: Maintained vibrant cultural prominence, economic vitality, and international recognition, significantly supported by pilgrimage activity, maritime commerce, and ecclesiastical patronage.

• Basques (Navarre): Skillfully preserved regional autonomy, diplomatic neutrality, and stable governance under Charles II and Charles III, significantly influencing northern Iberian political coherence.

Long-Term Significance and Legacy

Between 1384 and 1395 CE, Atlantic Southwest Europe:

• Achieved Portuguese independence restoration, governance stability, and cultural revitalization under King John I of Aviz, significantly shaping Portugal’s enduring medieval legacy.

• Maintained decisive Castilian governance stability, territorial integrity, and strengthened regional identity under the Trastámara dynasty, significantly influencing Iberian geopolitical stability.

• Preserved Navarrese regional autonomy, diplomatic neutrality, and governance resilience under Charles III’s pragmatic diplomacy, significantly shaping northern Iberian geopolitical coherence.

• Experienced sustained economic revival, cultural renewal, and persistent governance stability, profoundly influencing the region’s late medieval historical trajectory.

This pivotal era decisively influenced regional identities, governance stability, economic continuity, and cultural resilience, profoundly shaping Atlantic Southwest Europe’s historical legacy.

The Role of the Bourgeoisie and Nobility in the 1383–1385 Crisis

During the Portuguese Interregnum (1383–1385), when João of Avis (later King João I) led the struggle for Portugal’s independence against Juan I of Castile, the kingdom’s social classes were divided in their loyalties.

The Bourgeoisie’s Financial Support for João of Avis

The bourgeoisie of Lisbon, enriched by commerce and maritime trade, viewed João of Avis as the best candidate to protect their economic interests and maintain Portugal’s independence. Recognizing the threat of Castilian rule, they:

• Donated substantial sums to fund João’s war efforts.
• Secured additional financial support from Porto, Coimbra, and Évora, strengthening the urban resistance against Castilian dominance.
• Supported the military mobilization necessary for João’s forces to challenge Castile.

The Divided Nobility: Feudal Loyalty vs. National Sentiment

Unlike the bourgeoisie, the majority of the Portuguese nobility sided with Juan I of Castile due to feudal customsand the oaths of vassalage they had sworn to the House of Burgundy.

• These Castilian-aligned nobles pledged their loyalty to Beatriz of Portugal, wife of Juan I of Castile, believing she represented the legitimate succession.
• As a result, Juan of Castile gained the support of fifty castles, reinforcing his control over noble strongholdsin Portugal.

However, a small but influential group of nobles rejected Castilian rule and embraced Portuguese national sentiment, joining João of Avis:

• Álvaro Pais, a strong advocate of Portuguese sovereignty, played a key role in rallying urban support.
• João Afonso sided with João of Avis, opposing the feudal influence of Castile.
• Nuno Álvares Pereira, Portugal’s greatest military commander, became João’s chief general, leading the Portuguese forces to victory at the Battle of Aljubarrota (1385).

The Outcome: Victory and Independence

The urban bourgeoisie’s financial backing and the loyalty of key noble figures enabled João of Avis to defeat Castile and secure Portugal’s independence. His triumph marked the rise of the House of Avis and the beginning of Portugal’s golden age of exploration and expansion.

The 1383–1385 Crisis: Portugal's Struggle for Independence

By the late 14th century, Europe was in a state of crisis, plagued by the Hundred Years' War, the Black Death, and widespread famine. In Portugal, the situation was no different—following the death of King Ferdinand I in October 1383, the kingdom faced a dynastic and national crisis that threatened its independence from Castile.

The Treaty of Salvaterra de Magos and Portuguese Discontent (1383)

• In April 1383, King Ferdinand I had signed the Treaty of Salvaterra de Magos with John I of Castile, ensuring that:
  • Princess Beatrice, Ferdinand’s only child, would marry John I of Castile.
  • The Portuguese Crown would pass to their descendants, effectively setting the stage for a dynastic union with Castile.
• The treaty excluded the Portuguese nobility and merchants from negotiations, enraging the population and fueling fears that Portugal would be absorbed into Castile.
• With no undisputed heir, Portugal entered an interregnum (1383–1385), with no recognized monarch.

The Assassination of Count Andeiro and the Rise of João of Aviz (December 1383)

• The first open act of rebellion occurred in December 1383, when João, Grand Master of the Order of Aviz(illegitimate son of Peter I of Portugal), led the assassination of Count João Fernandes Andeiro, a pro-Castilian noble.
• The merchants of Lisbon, outraged by Castilian influence, named João of Aviz "Rector and Defender of the Realm", making him the leader of the anti-Castilian resistance.

John I of Castile’s Invasion and the Portuguese Response (1384)

• John I of Castile refused to abandon his claim to the Portuguese throne and moved to secure power by forcing Queen Leonor Teles to abdicate.
• In April 1384, he launched a punitive expedition into Alentejo.
• His Castilian forces were met at the Battle of Atoleiros (April 1384) by a smaller Portuguese army led by Nuno Álvares Pereira, a brilliant general and loyal supporter of João of Aviz.
• Using English defensive tactics, Pereira’s well-positioned infantry repelled Castilian cavalry charges, reportedly without a single Portuguese casualty.

The Beginning of the Fight for Independence

• Though a tactical success, the Battle of Atoleiros did not end Castilian ambitions.
• John I of Castile prepared for a larger invasion, culminating in the siege of Lisbon (1384) and later, the Battle of Aljubarrota (1385), which would determine Portugal’s fate as an independent nation.

The 1383–1385 Crisis was more than just a succession dispute—it became a national struggle for Portugal’s sovereignty, ultimately leading to the rise of the House of Aviz and the consolidation of Portuguese independence.

The Siege of Lisbon and the Battle of Atoleiros (1384)

Following his invasion of Portugal in early 1384, Juan I of Castile sought to capture Lisbon, the kingdom’s capital, and secure the Portuguese throne for his wife, Beatriz of Portugal. In March 1384, he laid siege to Lisbon by land and sea, hoping to force a Portuguese surrender through starvation and military pressure.

The Battle of Atoleiros (April 1384): A Tactical Innovation

While Lisbon remained under siege, Nuno Álvares Pereira, the rising military commander of the Portuguese resistance, moved to confront a Castilian force advancing in the Alentejo.

• On April 6, 1384, at the Battle of Atoleiros, his small, outnumbered Portuguese army faced a larger Castilian force.
• Recognizing his numerical disadvantage, Nuno Álvares Pereira deployed his troops in defensive squares, a tactic inspired by English longbowmen formations used in the Hundred Years’ War.
• The Portuguese forces, composed mostly of dismounted cavalry, used field defenses to neutralize the Castilian charge, inflicting heavy losses without suffering significant casualties themselves.
• This decisive victory demonstrated the effectiveness of defensive formations, setting a precedent for later battles, including the Battle of Aljubarrota (1385).

The Plague Breaks the Siege of Lisbon (October 1384)

Despite the setback at Atoleiros, Juan I maintained the siege of Lisbon, pressing the city into a state of famine and desperation.

• The siege lasted for seven months, causing immense suffering within the capital.
• However, by October 1384, an outbreak of the plague devastated the Castilian army, forcing Juan I to abandon the siege.
• He retreated to Seville, where he began preparations for a second invasion in 1385.

The Path to Portuguese Victory

Though Castile had not yet given up, the failures at Atoleiros and Lisbon provided João of Avis and Nuno Álvares Pereira with the opportunity to strengthen their position. With the support of the Portuguese bourgeoisie, urban militias, and key nobles, João was soon proclaimed king (April 1385), setting the stage for the decisive Portuguese victory at Aljubarrota in August 1385.