The Unification of England & the Death of the Kingdom of Mercia

Once the dominant realm in England, in the late ninth century, the Kingdom of Mercia fell to predatory Viking invaders and the expansionary ambitions of Alfred the Great.

Mar 18, 2024By Michael McComb, MA History

death of mercia unification england


The unification of England is often seen as a solely West Saxon venture, leaving out the role of the Kingdom of Mercia. However, Mercia played a vital role as Wessex’s ally and partner in the fight against Viking invaders and in establishing a unified English kingdom. This article will show how Mercia was irreversibly changed from a mighty kingdom to an Earldom subject to the West Saxon Kings as a result of this process of unification.


The Kingdom of Mercia and the Great Heathen Army

Map of the Anglo-Saxon Kingdoms in England, by Earle Wilbur Dow, 1907, Source:


Ninth-century England comprised four kingdoms: East Anglia, Mercia, Northumbria, and Wessex. Despite a history of war, violence, and rivalry, the 840s-850s saw relatively peaceful relations between these kingdoms. This was likely motivated by a collective belief that Viking raiders were the real enemy.


By the mid-ninth century, these Scandinavian pirates had devastated several coastal regions of England. In response, Mercia began to work closely with its southern neighbor, Wessex. In the 850s, we see closer economic ties between the two kingdoms and more interaction between their nobles and the marriage of King Burgred of Mercia (852-874) to Æthelswith, the daughter of the King of Wessex, further strengthened relations.


Yet the invasion of the Great Viking Army in 865 would set England on an entirely new course. No longer content with loot and plunder, the Vikings began to conquer and settle. By 871, they had conquered East Anglia and Northumbria and received tribute payments from Mercia and Wessex. Mercia suffered a further setback in 874 when King Burgred was forced into exile by the Viking leaders in England. His successor, King Ceolwulf II (874-877/9), could only appease the invaders by giving up the eastern half of Mercia.

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Ealdormen Æthelred and Mercia’s Decline

Map of the route of the Great Heathen Army in England, by David Hill, 2022, Source: Wikimedia Commons


Wessex also struggled with Viking invasions, being attacked in 871, 875, 876, 877 and 878. However, under the leadership of King Alfred (871-899), the West Saxons decisively defeated the Viking army at the Battle of Ethandun 878. The defeated Guthrum accepted baptism, agreed to peace with Wessex and, with Alfred’s blessing, set himself up as the new King of East Anglia.


Meanwhile, Ceolwulf II disappeared from the historical record in 877. A successor, Æthelred, is not recorded until 881. He inherited a Mercia, now half its former size and at war with the Welsh — an easy target for future Viking attacks. Since he does not appear to have had any dynastic links to his predecessors, some may have seen him as illegitimate, and he likely faced internal opposition. After a conclusive defeat in his war with the Welsh at the Battle of Conway 881, Æthelred turned to Wessex for protection.


By 883, a land charter in Worcester, Mercia, records him governing as an “Ealdormen of Mercia…with the consent of King Alfred” (Ealdormen was the senior noble title in England). Alfred was no stranger to the Mercians; his sister (Burgred’s wife) was a former Mercian Queen; his wife, Ealhswith, was Mercian and her brother, Æthelwulf, was a prominent Mercian Ealdormen.


Alfred’s “Kingdom of the Anglo-Saxons”

Map of Britain in 886, “English Mercia and Wessex” shows Alfred’s kingdom, by Bodrugan, 2006, Source: Wikimedia Commons


The motivations for both men are clear. Æthelred received Alfred’s backing, protecting him from his domestic rivals within Mercia and the Welsh and Viking threats he faced. For Alfred, receiving Æthelred’s submission provided him with a valuable ally in the wars with the Vikings. This provided a framework for a Southern English-Christian coalition, which had shared anti-Viking goals and a desire for stability after a period of chaos.


The agreements made between Æthelred and Alfred are not immediately obvious. The aforementioned land charter of 883 tells us that by using the title “Ealdormen,” Æthelred recognized that he was no longer a king or an independent ruler. It also tells us that Æthelred acknowledged Alfred as his superior and perhaps his king.


However, by the late 880s, Alfred adopted the new title “King of the Anglo-Saxons” (Angles representing Mercia and Saxons representing Wessex). This demonstrated that Alfred’s perception of his agreement with Æthelred was not the annexation of Mercia into Wessex but rather the formation of a new kingdom with a pan-English/Anglo-Saxon identity.


The Status of Æthelred’s in Alfred’s Kingdom

Monogram Penny of Alfred the Great minted in London, c. 871-899, Source: The Royal Mint Museum, London


Æthelred’s status in Alfred’s new kingdom is challenging to define. Historian Tim Clarkson described him as a “King in all but name.” Indeed, he was called “King of the Mercians” by the late 10th-century chronicler Æthelweard. Despite this, he never personally used this royal title after his 883 agreement with Alfred.


Furthermore, there are many characteristics of traditional Anglo-Saxon kingship that Æthelred did not possess. For example, under Æthelred, the Mercians followed Alfred’s law code and minted coins on his behalf. Yet, in some respects, Æthelred remained the heir to his royal Mercian predecessors. He was the leader of the Mercian army and held his own court in Mercia rather than being a regular attendee at Alfred’s court. Reflecting this ambiguity are the several titles, which Æthelred used in his charters, including Chief, Ealdormen, Lord, Patricius, Ruler, and Subregulus. It is perhaps most appropriate to see his status as somewhere between a king and a powerful nobleman operating within the confines of Alfred’s kingdom.


Alfred’s Respect for Mercian Customs

Anglo-Saxon Charter of Æthelred and Ætheflæd in 901, photographed by Dudley Mies, 2014, Source: Wikimedia Commons


Alfred managed his relations with Mercia carefully, recognizing the need to respect their traditions and customs. We see this in Alfred’s law code, for example. Rather than imposing West Saxon law upon the Mercians, he formulated a new law code inspired by previous kings of Mercia and Wessex.


Another example is London. The town had previously been part of Mercia before it fell to Viking invaders in the early 870s. When Alfred captured London in the mid-880s, he handed it over to the protection of Ealdormen Æthelred, once again demonstrating his respect for Mercian traditions.


However, the greatest honor Æthelred received was his marriage to Alfred’s daughter Æthelflæd. This strengthened ties between the two men, who were now family. Also, Æthelflæd’s mother was from a respected Mercian family of royal descent, providing Æthelred with a degree of legitimacy he may have previously lacked in Mercia. This may be considered an insufficient exchange for Mercia’s loss of independence. However, Æthelred had to embrace the new reality of governing a weakened Mercia, which, above all else, needed stability and protection.


Edward, Æthelflæd and the Continued Alliance

Silver Penny of Edward the Elder minted in East Anglia, c. 920-924, Source:


Æthelred remained an ally of Wessex for the rest of his life. When Wessex was invaded by a Viking army from across the English Channel in 892, he stood with the West Saxons, leading the Mercian army to aid his father-in-law, culminating in the Viking defeat at the Battle of Butingdon in 893.


Alfred died in 899, being succeeded by his son, Edward, who re-established relations with Æthelred on the same terms as his father had. Edward even sent his eldest son, Æthelstan, to be brought up at the Mercian court. The success of this alliance was proved once again in 910, when the Viking army of York led an invasion deep into Mercia, only to be decisively crushed by joint Mercian-West Saxon forces at the Battle of Tettenhall, resulting in the death of three Danish Viking kings.


Æthelred’s death came the following year. With no male heir, the Mercian throne went to his wife. Æthelflæd’s succession was, in many ways, a sign of continuity. As Edward’s sister, she maintained links with Wessex. She had also previously led the Mercians on behalf of Æthelred when he was ill; furthermore, she was descended from the Mercian kings of old, giving her a legitimate claim to the Mercian throne.


The Conquest of the Danelaw 

Statue of Æthelflæd recently built outside Tamworth Railway Station to commemorate 1,100 years since her death, photographed by Anna Toone, 2018, Source: Wikimedia Commons.


The first four years of Æthelflæd’s reign consisted primarily of building fortifications on her border. Then, with her borders secure and the Danes weakened from Tettenhall, she and her brother began an offensive campaign into Viking-held territory. By 915, Edward had conquered Essex and established control of the towns of Hertford, Buckingham, and Bedford. After this, he followed up with the conquest of the kingdom of East Anglia and much of the East Midlands.


The contemporary Anglo-Saxon Chronicle describes Edward’s ruthlessness in taking the fortress of the King of East Anglia; “they broke into it [the fortress], and slew the king, and Earl Toglos, and Earl Mann his son, and his brother, and all them that were therein, and who were resolved to defend it.” Æthelflæd similarly made progress, capturing the fortresses of Derby (917) and Leicester (918). She also managed to form an alliance with the rulers of Scotland and Strathclyde in opposition to the Viking leader, King Ragnall of York.


By 918, Alfred’s children had taken back almost all of Southern England. Historian Frank Stenton described this military operation as “One of the best sustained and most decisive campaigns in the whole of the Dark Ages.” 


Edward’s Succession to Mercia and Ælfwynn’s Deposal

Remains of St Oswald’s Priory, Gloucester, where Æthelred and Æthelflæd were buried, photographed by Philafrenzy, 2013, Source: Wikimedia Commons


The harmony between the Mercians and the West Saxons would be briefly interrupted by the death of Æthelflæd in 918. Within months, a power struggle broke out between Edward and her daughter, Ælfwynn. Æthelflæd appears to have been grooming Ælfwynn for rule. She attended councils in Wessex in 903 and Mercia in 904 and 915. While Æthelflæd similarly was held in high status before she came to rule Mercia, this was only the case after marrying Æthelred.


Being involved in matters of state for an unmarried woman, as Ælfwynn was, was unprecedented and must be a sign of preparation for leadership. However, either by convincing the Mercian nobility or through more forceful measures, by the end of 918, Edward deposed Ælfwynn. The Anglo-Saxon Chronicle records that Ælfwynn “was deprived of all dominion over the Mercians and carried into Wessex,” adding that “all the population in Mercia turned to him [Edward].” Edward’s motives are not entirely certain. He may have been skeptical of Ælfwynn’s loyalty to Wessex. Or perhaps the Mercian nobility may have preferred Edward, who had already achieved great martial feats, as their leader to defend them from King Ragnall. Alternatively, Edward may have simply sought to exploit a moment of uncertainty in Mercia for his own ends.


An End to Mercian Autonomy 

Stained glass window showing Alfred and Edward, photographed by Paul Kelly, Wells Cathedral, Somerset, Source:


Rather than appointing a deputy to govern on his behalf, Edward assumed direct control of Mercia. This fundamentally changed the Mercian-West Saxon settlement established by Æthelred and Alfred in 883. Despite this radical shift, he continued the policy constructed by Æthelflæd in the north.


Working with his new northern allies, in 920, he convinced King Ragnall to agree to a peace treaty with Bamburgh, Mercia, Scotland, and Strathclyde. However, some of his new Mercian subjects were unhappy with his rule. It has suggested that Edward may have made land appropriations of Mercian estates to his West Saxon followers. He may have also initiated the division of Mercia into shires based on the West Saxon administrative model. This ignored the pre-existing organizational structure of Mercia, based upon ancient tribal groups.


To many in Mercia, Edward appeared not to be respecting their traditions and customs. A revolt at Chester in 924 demonstrated the popular discontent with his rule. While Edward defeated the uprising, he was fatally wounded during the campaign and died in July 924.


A Mercian Prince from Wessex

Frontispiece of Bede’s Life of St Cuthbert, showing King Æthelstan presenting a copy to Cuthbert, c. 930, Source: Wikimedia Commons


Edward’s death would again demonstrate the strain between the Mercians and the West Saxons, who each backed separate sons of his for the succession. Only when the West Saxon candidate, Ælfweard, died in August 924 was Edward’s kingdom restored, with Wessex accepting the Mercian candidate, Æthelstan, as their new king. Æthelstan appealed to both peoples, as he was a West Saxon by birth but had spent most of his life in Mercia.


This dualism he embodied was recognized by his coronation oath, pronouncing him as “equally” King of the Angles and the Saxons. Æthelstan did receive some hostility in Winchester from his younger half-brother, Edwin, and Bishop Frithestan. This, however, was not a feeling shared across Wessex, where Æthelstan could hold court and royal councils without issue.


After securing his kingdom, Æthelstan would look northwards and, in 927, conquered Northumbria. Thus, the new dividing line in English politics became the English of Mercia and Wessex and the Anglo-Scandinavians of Northumbria. By comparison, divisions between Mercia and Wessex seemed minute and irrelevant. The goal for the Southern English would now be to control their new northern subjects.


King Edgar and the Last Lords of Mercia

Depiction of King Cnut fighting Edmund Ironside in 1016, by Matthew Paris, c. 1200-1259, Source: Wikimedia Commons


Once the Northumbrians were pacified, the Mercian-West Saxon divide briefly returned during King Eadwig’s reign (955-959). However, this was a result of political rather than regional factionalism. His successor, King Edgar (959-975), oversaw a golden age of peace and stability, forming a more centralized government than achieved by his predecessors. This, along with the appointment of his kinsman and loyal follower, Ælfhere, as Ealdormen of Mercia, made Mercian separatism very unlikely.


Nevertheless, the position of Ealdormen of Mercia remained one of the most prestigious offices in the realm. Its holder would be a dominant figure in the Midlands and a senior royal counselor. Indeed, Ælfhere was referred to as the “Prince of the Mercian People.” Another Mercian Ealdormen was “Ealdormen over all the kingdom of the Mercians.” It was a position of such power that King Cnut (1016-1035) in 1017 and King William I (1066-1087) in 1071 broke the Mercian Earldom into smaller lordships. Both preferred not to give such power to any one individual.


The final Earl of Mercia was Edwin (1062-1071), brother-in-law of Harold Godwinson. His death, at the hands of his own bodyguard in 1071 after a failed revolt against William I, marks the end of the Earldom of Mercia.


Reflections on the Kingdom of Mercia 

Offa’s Dyke, a series of defensive earthworks along the Mercian-Welsh border, one of the lasting achievements of 8th century Mercia, 2021, Source: ITV


In one sense, Mercia had a rather sad story. From its period of domination of Southern England during the eighth century to the death of its last earl in 1071, fleeing from a foreign conqueror. It was a true fall from grace. However, Mercia made vital military and political contributions toward forming the Kingdom of England, giving it an enduring legacy.


The critical turning point in its history was the Viking invasions of the 860s-870s. These invasions left Mercia plundered and cut in half, with weak leadership. Æthelred decision to turn to Alfred for help may have been his only realistic choice. Yet, it was difficult to imagine this settlement lasting in the long term.


Mercia held an awkward position, and its West Saxon overlord would not always share Alfred’s diplomatic skills. Nor would the rulers of Mercia and Wessex always enjoy the positive relationship that Æthelred and Æthelflæd had with Alfred and Edward. Perhaps Mercia would either have to eventually separate from Wessex or be absorbed into a larger West Saxon-led kingdom. It would ultimately come down to Edward’s deposal of Ælfwynn in 918, which would settle the matter. Nevertheless, it took West Saxon rulers who could appeal to the Mercians, such as Æthelstan and Edgar, to provide a more sustained unity.

Author Image

By Michael McCombMA HistoryMichael is an aspiring writer and historian with a passion for Medieval England and a keen interest in the House of Wessex. He holds an MA in History from Manchester Metropolitan University and his dissertation was titled ‘To what degree was there unity between Mercia and Wessex from 850-930?’. He has also previously written for The Historian’s Magazine.