The capture of William I of Scotland, also known as William the Lion, marked a significant turning point in the Revolt of 1173–74. This rebellion was driven by discontent among Scottish nobles against King Henry II of England, who had exerted substantial influence over Scotland. The conflict saw a coalition of Scottish nobles collaborating with rebels from England, including the sons of Henry II, who sought to weaken their father's hold on power. Alnwick, a fortified castle in Northumberland, became the site of this crucial encounter. On July 13, William was taken prisoner as he attempted to reassert control and validate his claim to authority amid the chaos. His capture would ultimately lead to significant consequences for Scotland's political landscape.

Following his capture, William was forced to sign the Treaty of Falaise in 1174, which acknowledged English supremacy over Scotland. This agreement imposed heavy penalties upon Scotland and effectively turned the nation into a vassal state. The loss of William led to a period of instability and discontent among the Scottish people, as many viewed the treaty as a surrender of their hard-won liberties. This event, therefore, not only changed the trajectory of William's reign but also had profound implications for the future of Scottish independence. Despite his captivity, William would later regain his throne, but the consequences of this defeat would linger in Scottish political memory for generations to come.