What is the main conflict in A Distant Mirror: The Calamitous 14th Century by Barbara W. Tuchman?

The castle of Coucy is a huge building on a hilltop in Picardy. There are five towers and a donjon—a central citadel—capable of housing a thousand people, even for a prolonged period such as during a siege. The castle is built in 1223 while there are many great buildings being constructed. Most take many years for completion but the castle at Coucy is finished in seven years. It is said there is a famous motto attached to the castle that reads: "Not king nor prince, Duke nor count am I; I am the lord of Coucy."

Into this life Enguerrand VII is born as ruler of Coucy.