The Tree of Battles was written by Honore Bonet in the latter part of the 14th century. Bonet was Priest that served the Abbey of L'Isle Barbare at Lyons, France.The Tree of Battles is a treatise, a book, that outlines the codes and conducts of war, knightly combat. Written not to be a code, but a cure to the many wars of the time, its author had the intent to bring Christian Europe, specifically France together. What it rapidly became however was the cornerstone for Knightly Combat and Battle. It is a marvelous read, if you can get a copy of it, give it a shot!
Some questions posed:
"Whether it is fitting for a King or Prince b deceit or subtlety to overcome another Prince his enemy and in what way he may offend in this matter."
"Whether vassals should go to war for their Lord at their own expense."
The Tree of Battles.