Never as neat or well organized as many descriptions suggest, in essence feudalism involved the exchange of grants of land for military and political… - Marilyn Stokstad

The Church attempted to regulate this rather violent society, and eventually a code of honor evolved known as the code of chivalry. (...) Those who aspired to be knights had to have aristocratic ancestors and wealth enough to own warhorses and armor and to provide for a team of supporters.

As they captured each territory, William and his men secured their camps with simple earth and timber defenses characteristic of northern Europe (...). These wooden structures have disintegrated, but sometimes their earthen mounds survive as rolling hills or picturesque elements in the landscape. Timber castles were especially useful to a warrior king like William the Conqueror who moved rapidly to bring new territories under control. The earth and timber castles could be built quickly, since the newly moved earth did not have to support great weight. Such structures were also relatively cheap because they required no specialized masons and expensive stone. Since the timber building tradition was widespread both in the British Isles and on the continent, the carpenters knew the building techniques. These castles were essentially towers and stockades; they provided garrison headquarters as well as residences.

Just as towers and crenellations indicated a building’s status, so the crenellated wall signified a castle in the visual arts and in that distinctive medieval sign language known as heraldry. The heraldic symbol of the kingdom of Castile, for example, consisted of a wall and three crenellated towers. This simple composition was easily recognized and reproduced.