This book provides a concise and incisive introduction to the knights of the Teutonic Order, the last of the great military orders established in the twelfth century. The book traces the Order's evolution from a crusader field hospital into a major territorial ruler in northeastern Europe. Notably, the knights constructed distinctive fortified convents, including their headquarters in Western Christendom's largest castle. The narrative concludes with the Order's fifteenth-century decline due to the combined effects of a devastating war with Poland-Lithuania and the Protestant Reformation. The result is an accessible overview of this pivotal corporation in European history.