The local strongmen of Norse societies built strongholds for their base of operation. This was a strong defensive structure that they could defend and where they could store their food and treasure. Such strongmen surrounded themselves with elite warriors, like Huskarls and Jarls, which they supported with booty and land.

The earliest castles found in northern Europe, and especially Britain, were called motte and baileys. The motte was a hill, sometimes manmade, and the bailey was a courtyard with a palisade wall around the motte. The motte was defended by a wooden tower that eventually evolved into the keep that was the central building in later medieval castles.