BattlefieldsBattle of Caer Gybi
Early Medieval

Battle of Caer Gybi

877
Anglesey, Wales
Also known as: Viking attack on Holyhead late 9th century
Era
Early Medieval
Battle Type
Naval Engagement
Location
Anglesey, Wales
Status
Unregistered
The Combatants

Who Fought

Defeated
Gwynedd (Rhodri Mawr)
Forces
Gwynedd c.500–800; naval engagement
VS
Victor
Vikings / Norse
Forces
Vikings/Norse c.800–1200
Outcome
Viking victory; Rhodri defeated and driven to Ireland; Anglesey occupied briefly
The Battle

History & Significance

In 877, a Danish force aided by the Mercian king Ceolwulf defeated Rhodri Mawr at the "Battle of Sunday" and seized Anglesey, compelling him to flee to Ireland. The fort at Caer Gybi (Holyhead) — built within the walls of a Roman shore fort — was a focal point for defence of the north-west coast. Rhodri returned from Ireland the following year and won a battle to recover Anglesey before being killed by Mercians later in 878.

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