Dr. Claussen is a medieval European historian.  His research deals with violence, religion, and chivalry in medieval Castile and its place in the wider Mediterranean and Atlantic worlds.  Dr. Claussen works to understand the ideas of knights and men-at-arms in the medieval world through an examination of traditional historical sources such as chronicles, treatises, and the records of central government, but also through literary and imaginative sources such as frontier ballads, poetry, and chivalric romance.  In a broader sense, Dr. Claussen is a historian of violence writ large, seeking to understand the human history of brutality and the way in which various peoples over time have embraced, rejected, reformed, and redirected the violent impulses of society.