After delving into some family history I recently discovered that I may have had ancestors in the Teutonic Order. What are some good books and resources on the Teutonic Knights?
For the Teutonic Order, William Urban is the Grand Master (eh)
The best introduction is William Urban's The Teutonic Knights: A Military History; that covers the the establishment of the Order, its political and military history and the eventual fall of the Order-State.
He also has a book more focused on the last years of the Teutonic Knights as a military & political force called... The last years of the Teutonic Knights
Urban has more academic books focused on the specific crusades but they're expensive and nerdy.
Then 2 non Urban books that give a fantastic overview of all the Monastic Military Orders and the Northern Crusades are
The Monks of War by Desmond Seward
And The Northern Crusades by Eric Christiansen