Norman motte and bailey castles were introduced which reshaped warfare in England, reducing the necessity for and risk of large-scale field engagements. the system of feudalism developed as William gave out lands in return for military service (either in person or a force of knights paid for by the landowner).

The introduction of Norman castles following the 1066 invasion fundamentally transformed England's physical and social landscape. Unlike the Anglo-Saxon "burhs," which were large fortified towns intended to protect the community, Norman "motte-and-bailey" castles were private, garrisoned fortresses designed for military control and psychological intimidation of the local population. These structures allowed a small Norman elite to govern vast, often hostile, territories. Architecturally, the transition from wooden mounds to massive stone keeps like the White Tower (Tower of London) introduced Romanesque styles and advanced masonry to the British Isles. Socially, castles became the administrative hubs of the feudal system, where land was held in exchange for military service. By the 12th century, these castles acted as the backbone of royal and baronial authority, dictating the growth of nearby towns and ensuring that power remained centralized in the hands of the Norman aristocracy for centuries to come.