William had to to secure his foothold in southern England, and required a means of ruling the rest of his new country. As a result, from 1066 to 1087 William and the Normans built nearly 700 motte and bailey castles across England and Wales.

William the Conqueror is credited with initiating a "castle-building revolution" in England following the Norman Conquest of 1066. While historical records vary, he is directly responsible for commissioning at least 36 major stone and timber castles personally, but his broader campaign of subjugation led to the construction of approximately 500 to 1,000 "motte-and-bailey" castles by his loyal barons across the English landscape. His most famous personal project is the Tower of London (specifically the White Tower), which was designed to overawe the rebellious citizens of London. Other iconic strongholds built during his reign include Windsor Castle, Warwick Castle, and Colchester Castle. These structures were not just military fortifications; they were psychological tools used to assert Norman dominance over the Anglo-Saxon population. Most of these early castles were initially made of wood for speed and were later rebuilt in stone. By the time of his death in 1087, the English skyline had been permanently altered, marking the transition from an unfortified landscape to one defined by the feudal power of the Norman castle.