Æthelstan's invasion of Scotland
In the early 10th century, Æthelstan, the first King of England, embarked on a series of military campaigns to assert his dominance over the northern kingdoms, culminating in his invasion of Scotland in 934. Motivated by territorial ambitions and to subdue potential threats, Æthelstan launched a two-pronged assault: a land-based invasion through Northumbria and a naval attack along the eastern Scottish coast. The reasons for the invasion remain debated among historians, with suggestions ranging from retaliation for Scottish support of Norse raiders to Æthelstan's broader imperial ambitions. While the campaign did not result in permanent English control of Scottish territories, it did solidify Æthelstan's position as the preeminent ruler in Britain and forced Scottish King Constantine II to recognize his overlordship, at least temporarily.
This event is also available in the following timelines: