TRINODA NECESSITAS

The Anglo-Norman Kings could expand their workforce without having to hire labour.The trinoda necessitas, of which fyrd service was one, included the burden of brigbot and burbot-bridge building and fortress building. This usually meant that those lower on the social ladder, from village and lordship were obliged to supply the labour.In Anglo Saxon times this provided only for town, or burg defense. This device was used by the conqueror and his henchmen to erect Royal and private castles. Failure to perform the duty was subject to royal jurisdiction, complete with fine. A feudal obligation to act as castle guard also existed.

In the late 11th Century a crusade was mounted to the holy land which would become known in later generations as the "first" crusade. 

This crusade was to have an effect on castle building both in England an Europe on the whole.  In 1066 there was probably only a half dozen castles in England which would grow to more than 5oo by the turn of the century.

In the beginning most were constructed of timber as in the original Motte and Bailey style. When the crusaders arrived in the holy land, they stayed but a short time, leaving the maintenance and control to the Templars and hospitallers. These made good use of the masonry skills of their sometimes allies the Greeks and also that of their enemies the Turks. The new castles were strong and complicated right from the start. Over the next century the new skills spread to Europe, and nearly all castles were converted to stone. As castles became stronger, the siege tactics became even more fearful. Huge siege engines such as the trebuchet were often built on site, then used to batter the castle walls down. Use the link on the left to learn more about siege engines.