The establishment of the Korean kingdom of Baekje in 18 BCE heralds the beginning of the Three Kingdoms period.

According to the Samguk Sagi, the founder of Baekje is Onjo, the third son of Goguryeo's founder Jumong and So Seo-no, who leads a group of people from Goguryeo south to the Han River basin.

According to the Chinese record San Guo Zhi, during the Samhan period, one of the chiefdoms of the Mahan confederacy was called Baekje.

According to the detailed account in the Samguk Sagi, Jumong had left his son Yuri in Buyeo when he left that kingdom to establish the new kingdom of Goguryeo.

Becoming King Dongmyeongseong, Jumong had two more sons with So Seo-no, Onjo and Biryu.

When Yuri later arrived in Goguryeo, Jumong promptly made him the crown prince.

Realizing Yuri would become the next king, So Seo-no left Goguryeo, taking her two sons Biryu and Onjo south to found their own kingdoms with their people, along with ten vassals.

She is remembered as a key figure in the founding of both Goguryeo and Baekje.

Onjo settles in Wiryeseong (present-day Hanam), and calls his country Sipje (meaning "Ten Vassals"), while Biryu settleds in Michuhol (present-day Incheon), against the vassals' advice.

The salty water and marshes in Michuhol make settlement difficult, while the people of Wiryeseong live prosperously.

Biryu then goes to his brother Onjo, asking for the throne of Sipje.

When Onjo refuses, Biryu declares war, but loses.

In shame, Biryu commits suicide, and his people move to Wiryeseong, where King Onjo welcomes them and renames his country Baekje ("Hundred Vassals”).

Under pressure from other Mahan states, King Onjo moves the capital from the south to the north of the Han river, and then south again, probably all within present Seoul.

The Middle East: 21–10 BCE

Stabilization and Diplomatic Consolidation

In 20 BCE, tensions between Rome and Parthia ease significantly following successful diplomatic negotiations led by Augustus. To solidify this diplomatic understanding, Phraates IV returns the Roman standards previously captured from Crassus at the Battle of Carrhae (53 BCE) and from Mark Antony's campaign (36 BCE). This symbolic act restores Roman pride and greatly enhances Augustus’s prestige in Rome, reinforcing his image as a powerful yet prudent leader who achieves victory through diplomacy rather than warfare.

Phraates IV further solidifies peace by sending several of his sons as hostages to Rome, a common practice meant to guarantee good behavior between powerful empires. These royal hostages not only serve as assurances against future conflicts but also as a bridge for cultural and political exchanges between Parthia and Rome.

Meanwhile, Parthia itself enjoys a period of relative stability and internal consolidation under Phraates IV, despite lingering discontent among certain segments of the nobility. The empire continues to benefit economically from its strategic control of trade routes linking the Mediterranean world with Central and South Asia, ensuring the region's continued prosperity.

In the broader Near East, Roman influence steadily expands through a careful blend of direct control and client kingships, with client rulers managing local affairs under Roman oversight. This era thus marks a critical phase of diplomatic stability and controlled expansion, emphasizing the Roman Empire's strategic preference for maintaining peace and influence through carefully managed alliances and diplomacy rather than outright conquest.

Brass is available in sufficient supply by the first century BCE to use as coinage in Phrygia and Bithynia, and after the Augustan currency reform of 23 BCE it is also used to make Roman dupondii and sestertii.

The uniform use of brass for coinage and military equipment across the Roman world may indicate a degree of state involvement in the industry.

The yoke of empire on Greece is relatively light; many Greek cities approve the new order set forth by Augustus.

Rome demands only two things from its Greek holdings: security and revenue.

In Athens, which enjoys imperial favor, a spacious market for the sale of oil and other commodities is laid out east of the old Agora with funds originally provided by Caesar and supplemented by Augustus.

In the old Agora itself, the emperor’s deputy Agrippa builds a new odeum, or concert hall, in the middle of the square.

A large building, perhaps a law court, is also erected at the northeast corner.

On the Acropolis, a small round temple is erected to the goddess Roma and the emperor Augustus.

Mediterranean Southwest Europe (21–10 BCE): Augustus and the Foundation of Caesaraugusta

The era 21–10 BCE highlights Augustus’s profound influence on Roman territorial and urban expansion, marked notably by the strategic foundation of new cities in Iberia, reinforcing Rome’s imperial transformation through colonization and consolidation.

Foundation of Caesaraugusta

During this period, Augustus founds Caesaraugusta—modern-day Zaragoza—in Iberia, strategically establishing a city to settle veterans from the Cantabrian Wars. Caesaraugusta occupies the site of the ancient Iberian village Salduie(known as Salduba in Roman sources), representing Rome's policy of rewarding military service and ensuring territorial stability.

Although the exact date of Caesaraugusta’s founding remains uncertain, historical evidence places it confidently between 25 BCE and 12 BCE. This urban development exemplifies the broader Roman effort to solidify control and integrate conquered territories into the imperial structure.

Veteran Settlements and Romanization

The establishment of veteran colonies such as Caesaraugusta is a deliberate strategy employed by Augustus to anchor Roman authority in newly acquired regions. By settling Roman citizens—particularly veterans—in these territories, Augustus ensures the proliferation of Roman culture, law, and governance, significantly influencing the historical trajectory of Iberia.

Administrative Consolidation and Governance

Augustus continues his administrative reforms, improving provincial governance by enhancing local autonomy, efficiency, and reducing corruption. These measures strengthen Rome’s administrative framework, promoting economic prosperity and societal stability throughout the provinces.

Cultural and Ideological Patronage

Augustus’s rule also sustains significant cultural patronage, promoting literature, arts, and public architecture to emphasize imperial values of peace, prosperity, and moral integrity. Such cultural projects reinforce Augustus’s image as the restorer of Roman traditions and virtues.

Legacy of the Era

The era 21–10 BCE exemplifies Augustus's strategic approach to empire-building through urban foundations and veteran settlements, laying robust foundations for Roman influence in Mediterranean Southwest Europe. These actions significantly contribute to Rome’s long-term stability and the consolidation of imperial authority.

The Sedetani, a tribe of ancient Iberians, populated a village called Salduie, Salduba in Roman sources, where Augustus founds a city called Caesaraugusta to settle army veterans from the Cantabrian wars.

The foundation date of Caesaraugusta has not been set with total precision, though it is known to lie between 25 BCE and 12 BCE.

North Africa (21–10 BCE)

Roman Provincial Enhancement, Mauretanian Cultural Flourishing, Cyrenaic Stability, Berber Integration, and Saharan Connectivity

Roman Governance and Economic Consolidation

Between 21 and 10 BCE, Roman administrative control over Africa Proconsularis becomes increasingly robust, driven by enhanced investments in infrastructure, agricultural improvements, and urbanization. Cities such as Utica continue to thrive as central administrative and commercial hubs, deeply embedding North Africa within Rome’s expansive Mediterranean economic and administrative network.

Numidia: Continued Stability and Economic Growth

Numidia sustains its integration as a key Roman province, experiencing continued economic stability and growth. Structured Roman governance facilitates increased agricultural productivity, efficient regional trade, and infrastructure enhancements. Numidian society maintains its unique cultural identity within the broader Roman framework, contributing significantly to provincial cohesion and stability.

Mauretania: Cultural Prosperity under Juba II and Cleopatra Selene

Under the cultured and scholarly leadership of King Juba II, Mauretania continues its remarkable cultural and economic flourishing. Initially restored as the King of Numidia (29–27 BCE) by Augustus, Juba's loyalty and military service, notably in Spain, earn him the kingship of Mauretania. Augustus further solidifies Juba's rule by arranging his marriage between 26 BCE and 20 BCE to Cleopatra Selene II, daughter of Cleopatra VII, providing her with a substantial dowry and appointing her queen.

Unable to return to Numidia due to its provincialization in 46 BCE, Juba and Cleopatra Selene establish their residence in Mauretania, an unorganized territory requiring Roman oversight. They rename their capital Caesarea (modern Cherchell, Algeria) in honor of Augustus. The city, strategically located along vital Atlantic and Mediterranean trade routes, undergoes extensive cultural enhancement. Juba embellishes Caesarea and another city, Volubilis, with baths, theaters, and sophisticated architectural and sculptural projects combining Egyptian, Greek, and Roman styles.

Cleopatra Selene significantly influences Mauretanian policy, guiding the kingdom toward remarkable prosperity. The fertile lands produce valuable commodities such as grain and olive oil, which are exported extensively across the Mediterranean, contributing to Mauretania’s wealth and prominence as a vital client-kingdom within Rome's geopolitical landscape.

Cyrenaica: Sustained Economic and Intellectual Prosperity

Cyrenaica maintains its robust economic performance under stable governance. The Greek Pentapolis—Cyrene, Barce (Al Marj), Euhesperides (Benghazi), Teuchira (Tukrah), and Apollonia (Susah)—continues thriving economically, particularly through sustained trade in grain, wine, wool, livestock, and the highly valued medicinal herb Silphium.

Cyrene remains an esteemed center of learning, continually attracting prominent scholars, philosophers, and medical practitioners. Its educational, medical, and cultural institutions persist as influential nodes within broader Mediterranean intellectual and cultural networks.

Berber Communities: Continued Integration and Cultural Resilience

Berber communities remain deeply integrated economically within Roman and broader Mediterranean trade networks. Coastal economic hubs, particularly Oea (Tripoli), maintain vibrant trade activities, indirectly supporting inland Berber populations.

Inland Berber tribes sustain traditional governance and cultural practices, benefiting from thriving coastal economic exchanges. This ongoing interconnection ensures sustained regional stability, underpinning Berber resilience and economic continuity.

Garamantes and Saharan Trade Networks

The Garamantes persist as pivotal facilitators of trans-Saharan trade, significantly contributing to regional prosperity through extensive commerce. Their advanced agricultural techniques sustain major Saharan settlements, reinforcing the importance of their role in connecting sub-Saharan and Mediterranean markets through trade in gold, salt, ivory, slaves, and exotic goods.

Musulami, Gaetulians, Mauri (Moors), and Saharan Pastoral Nomads

The Musulami, situated between Numidia and the Sahara, actively participate in agriculture and pastoralism, fostering continued commercial and cultural interactions with Roman and Numidian communities.

The Gaetulians remain influential through their semi-nomadic pastoral lifestyle, significantly facilitating trade and cultural exchanges across inland and coastal territories.

The Mauri (Moors), inhabiting western regions adjacent to Mauretania, sustain their regional influence through ongoing diplomatic and commercial activities, contributing notably to local stability and economic vitality.

Saharan pastoral nomads persist as essential connectors of varied ecological and economic zones. Their transhumant practices enhance trade, cultural exchange, and knowledge dissemination, further strengthening North Africa’s interconnected communities.

Cultural Syncretism and Interaction

Continued interactions among Berber, Roman, Greek, Garamantian, Musulami, Gaetulian, Mauri, and Saharan pastoral populations enrich regional traditions in crafts, art, and artisanal production. Religious syncretism remains vibrant, harmoniously integrating indigenous beliefs with Roman, Greek, Phoenician, and Saharan practices, contributing to North Africa’s diverse cultural richness.

Stable Foundations and Sustained Prosperity

By 10 BCE, North Africa demonstrates continued prosperity and stability through strengthened Roman provincial governance, Juba II and Cleopatra Selene’s culturally vibrant Mauretania, sustained Cyrenaic prosperity, resilient Berber communities, and dynamic Saharan trade and pastoral networks. Collectively, these interconnected factors secure North Africa's long-term prominence within the evolving Mediterranean geopolitical context.

Juba II, who Augustus had restored as the king of Numidia between 29 BC – 27 BCE, had established Numidia as a Roman ally; he is to become one of the most loyal client kings that serves Rome.

Between 26 BCE and 20 BCE, Augustus has arranged for him to marry Cleopatra Selene II, giving her a large dowry and appointing her queen.

It is probably due to his services with Augustus in a campaign in Spain that lead Augustus to make him King of Mauretania.

By then her brothers, Alexander Helios and Ptolemy Philadelphus, have died, probably from illness.

When Cleopatra marries Juba, she is the only surviving member of the Ptolemaic dynasty.

Juba and Cleopatra cannot return to Numidia, as it had been provincialized in 46 BCE.

The couple is sent to Mauretania, an unorganized territory that needs Roman supervision.

When the couple moves to Mauretania, they rename their new capital Caesaria (modern Cherchell, Algeria) in honor of Augustus.

The construction and sculpture projects at Caesaria and …

…another city, Volubilis, display a rich mixture of Egyptian, Greek and Roman architectural styles.

The fertile lands of the province produce many commodities such as grain and olive oil, contributing to the province's wealth and prosperity.

Cleopatra is said to have exercised great influence on policies that Juba creates.

Through her influence, the Mauretanian Kingdom flourishes, exporting and trading throughout the Mediterranean.

Atlantic Southwest Europe (21–10 BCE): Consolidation of Roman Rule and Provincial Stability

Between 21 and 10 BCE, Atlantic Southwest Europe—covering northern and central Portugal, Galicia, Asturias, Cantabria, and northern Spain south of the Franco-Spanish border (43.05548° N, 1.22924° W)—entered a period marked by comprehensive consolidation of Roman provincial authority following the decisive conclusion of the Cantabrian Wars. Roman governance stabilized significantly, facilitating extensive economic integration into Mediterranean networks, deepening reliance on slavery, and reshaping regional social structures. Nonetheless, indigenous cultural traditions and regional identities persisted robustly, adapting dynamically under full Roman imperial administration.

Political and Military Developments

Roman Administrative Stabilization and Provincial Integration

• Following the conclusion of the Cantabrian Wars, Roman provincial authority was solidified across the entirety of Atlantic Southwest Europe. Roman governance structures, including provincial administration, permanent military garrisons, and fortified urban centers, secured stable control and reduced localized resistance significantly.

• Augustus’s administrative reforms introduced consistent governance, enabling sustained peace, efficient resource management, and internal stability throughout the region.

Northern Regions: Transition from Resistance to Accommodation

• Tribes formerly resistant to Roman rule, particularly the Gallaeci, Astures, and Cantabri, began transitioning toward acceptance of Roman provincial structures, though with occasional localized resistance. The construction of strategic fortifications and Roman military roads facilitated rapid deployment of troops, securing Roman control and encouraging tribal adaptation.

• The Vascones solidified their diplomatic neutrality, preserving territorial autonomy and distinct cultural identity within a stable Roman provincial environment.

Economic and Technological Developments

Comprehensive Mediterranean Economic Integration

• Economic integration into Roman-dominated Mediterranean trade deepened further, transforming local economies into specialized suppliers of metals (silver, copper, tin), salt, agricultural produce, timber, livestock products, textiles, and slaves. The importation of Mediterranean luxury items, ceramics, wine, olive oil, and advanced iron products became commonplace.

• Local elites and new provincial classes increasingly benefited from these trade exchanges, reinforcing social stratification, economic specialization, and regional dependency on Roman economic networks.

Deepening Reliance on Slave Labor

• Slavery remained central to regional economies, widely utilized in mining, agriculture, artisanal production, domestic labor, and urban infrastructure projects. A thriving slave trade became permanently embedded within the regional economic structure, deeply influencing social hierarchies and economic patterns.

Technological Advancements in Metallurgy and Infrastructure

• Metallurgical technology, particularly ironworking, advanced significantly, improving agricultural productivity, artisanal capabilities, and regional infrastructure development. Local artisans, notably among Lusitanians, Vettones, and Gallaeci, produced high-quality weaponry, armor, agricultural tools, and decorative objects, integrating local and Roman-influenced techniques.

Cultural and Religious Developments

Continued Cultural Identity and Artistic Synthesis

• Regional material culture retained strong indigenous Iberian and Celtic elements, increasingly integrated with Roman artistic traditions. Artistic expressions—such as sophisticated metalwork, decorative jewelry, pottery, ceremonial artifacts, and household objects—reflected continuing regional pride and cultural identity.

• Despite comprehensive Roman provincial authority, cultural identities—particularly among the Gallaeci, Astures, Cantabri, and Vascones—remained resilient, dynamically adapting within a Romanized context.

Ritual Continuity and Adaptations

• Religious practices persisted and adapted, blending indigenous Iberian, Celtic, and Roman religious traditions. Established sacred landscapes, sanctuaries, and ritual practices continued actively, fostering communal cohesion and cultural continuity.

• Ancestral rites, communal festivals, and warrior traditions endured, reinforcing regional identity and social cohesion under stable Roman governance.

Notable Tribal Groups and Settlements

• Lusitanians: Fully integrated into the Roman provincial framework, benefiting economically and culturally from stable administrative structures.

• Vettones and Vaccaei: Successfully maintained territorial integrity, economic prosperity, and local autonomy through strategic collaboration with Roman authorities.

• Gallaeci, Astures, Cantabri: Transitioned gradually from persistent resistance to cautious adaptation, increasingly cooperating with Roman provincial administration.

• Vascones: Solidified diplomatic neutrality, preserving territorial autonomy, cultural distinctiveness, and internal stability under Roman rule.

Long-Term Significance and Legacy

Between 21 and 10 BCE, Atlantic Southwest Europe:

• Underwent comprehensive stabilization under Roman provincial rule, reshaping regional political, economic, and social structures profoundly.

• Solidified long-term economic integration into Mediterranean trade networks, permanently embedding slavery as a key economic institution.

• Demonstrated resilient cultural identities, dynamically adapting local traditions within a stable Roman administrative context, shaping long-term regional identity and cultural adaptation processes.

This era definitively established Roman authority, facilitating a lasting period of stability, economic prosperity, and cultural integration, significantly influencing the historical trajectory of Atlantic Southwest Europe under the Roman Empire.