The campaigns of Edward the Elder and his sister Aethelflaed, Lady of the Mercians, were decisive in the long struggle to reclaim and consolidate English control over the Danelaw in the early 10th century.

Background to the Conquest of the Danelaw

The Danelaw was the region of England under Danish control, established following the Viking incursions of the late 9th century. By the early 900s, it was still dominated by Scandinavian rulers, but political fragmentation and the growing strength of Wessex and Mercia offered opportunities for reconquest. Edward the Elder (King of Wessex, 899–924) inherited his father Alfred’s military reforms and strategic vision, while Aethelflaed—widow of Æthelred, Lord of the Mercians—ruled Mercia effectively, often acting in military partnership with her brother.

Strategic Context and Objectives

Edward and Aethelflaed’s ultimate goal was the reunification of England under Anglo-Saxon control. The Danelaw posed both a military and political challenge:

• Military threat from Danish armies in Northumbria and the East Midlands.

• Political fragmentation within Viking territories created chances for local submissions.

• The need to secure fortified burhs as strongholds from which to project power.

They pursued a two-pronged approach: Edward focused on the eastern frontier and East Anglia, while Aethelflaed targeted the Midlands and north.

The Burh-Building Campaign

Both rulers utilised and expanded the burghal system developed under Alfred.

View along the Wareham earthwork rampart, showing the height and profile of an Anglo-Saxon burh defence. This illustrates how a burh functioned as a fortified base for defence and control. The photograph shows modern paths and vegetation; the site itself predates Edward and Aethelflaed but exemplifies the fortification style their campaigns employed. Source

Burhs served as fortified centres for:

• Defence against Viking raids.

• Bases for launching counterattacks.

• Administrative hubs to project royal authority.

Between 910 and 920, Edward built or restored burhs at sites including Hertford, Witham, and Maldon in Essex, while Aethelflaed developed strategic positions at places such as Tamworth, Stafford, and Warwick.

Diagrammatic map of Anglo-Saxon burhs named in the Burghal Hidage. It illustrates how fortified centres underpinned defence and reconquest operations in the early 10th century. Some burhs shown fall outside Edward and Aethelflaed’s immediate theatres, providing wider context for the system as a whole. Source

Key Campaigns of Aethelflaed

Aethelflaed’s military skill and political diplomacy were pivotal:

• 910 – Joint West Saxon–Mercian forces defeated a major Viking army at the Battle of Tettenhall, crippling Danish power in the Midlands.

• She captured key strongholds such as Derby (917) and Leicester (918), undermining Viking control in the Five Boroughs.

• Through diplomacy, she secured the submission of Danish leaders in several towns without direct conflict.

• Shortly before her death in 918, she had gained the allegiance of the Northumbrian Danes, though this did not result in full control.

Edward’s Eastern Campaigns

Edward coordinated his campaigns to complement Aethelflaed’s northern advances:

• Targeted Viking bases in East Anglia and Essex.

• Constructed and garrisoned burhs to protect captured areas.

• Achieved the submission of East Anglian leaders and extended control along the eastern coast.

• Integrated newly conquered regions through settlement and fortification rather than relying solely on garrisons.

The Five Boroughs and Strategic Importance

The Five Boroughs—Derby, Leicester, Lincoln, Nottingham, and Stamford—were central to Danelaw power in the Midlands.

Map of the English Midlands c. 912 highlighting The Five Boroughs and neighbouring Anglo-Saxon and Danish polities. This clarifies the geography that Edward and Aethelflaed exploited during their coordinated offensives. The legend and surrounding labels add broader regional context beyond the minimum syllabus detail. Source

• Aethelflaed’s capture of Derby and Leicester weakened Viking cohesion.

• Edward’s influence ensured the eventual incorporation of all five boroughs into Anglo-Saxon control.

• Their loss deprived the Danes of major administrative and military centres.

Co-ordination Between Wessex and Mercia

Edward and Aethelflaed’s campaigns were closely coordinated despite operating from separate realms:

• Simultaneous offensives applied pressure from multiple directions.

• Mutual defence pacts allowed rapid reinforcement.

• Burhs built by one ruler often supported the operations of the other.

The partnership was strengthened by shared strategic aims and familial trust, enabling an unusually united Anglo-Saxon war effort.

Political Submissions and Diplomacy

Military action was accompanied by efforts to secure oaths of allegiance from local rulers:

• Many Danish leaders recognised Edward’s overlordship to preserve their lands.

• Submission often meant swearing loyalty, paying tribute, and accepting Anglo-Saxon legal authority.

• These arrangements stabilised newly conquered areas without prolonged occupation.

The Role of Logistics and Resources

The success of the campaigns relied on:

• Efficient mobilisation of the fyrd (levy-based army) for both short-term raids and extended sieges.

• The capacity to garrison burhs and maintain supply lines.

• Economic resources from taxation and trade to sustain military operations.

Well-organised supply routes ensured that forces could remain in the field for extended periods, giving the Anglo-Saxons a strategic advantage over Viking raiders.

The Death of Aethelflaed and Edward’s Consolidation

Aethelflaed’s death in 918 marked a turning point:

• Edward swiftly moved to take direct control of Mercia, ensuring unity of command.

• He continued to press campaigns northwards, securing further Viking submissions.

• His authority by 920 extended over much of England south of the Humber, setting the stage for later advances into Northumbria.

Outcomes of the Conquest of the Danelaw

By the early 920s:

• The majority of the Danelaw south of the Humber was under Edward’s rule.

• Viking political dominance in central England was broken.

• The Anglo-Saxon kingdoms of Wessex and Mercia were effectively united, forming a strong foundation for later kings to claim overlordship over all England.