Norman castles were a foreign intrusion on the British landscape. The signature Saxon defensive structure was the burh, a fortified settlement that protected ruler and ruled alike. The Normans, greatly outnumbered by a hostile native population, used earthwork motte-and-bailey structures for the first-wave of subjugation, following up with massive ‘statement’ stone castles. Chronicler William of Newburgh termed them the ‘bones of the kingdom’, clustered in areas of repeated irruptions of rebellion and turmoil, most notably the Welsh Marches. A fresh impetus occurred during the Anarchy of King Stephen’s reign (1135–54) when, according to the Anglo-Saxon Chronicle, rebel nobles ‘cruelly oppressed the wretched people with castle-works… and filled them with devils and wicked men’. Witnessing their effectiveness, rivals began to imitate the Normans: the Welsh princes were soon building their own castles. In Scotland, David I (1124–53) invited Norman castle-builders to settle, particularly in Galloway, to pacify unruly locals.