The popes are challenging the power of the secular rulers of Europe, especially the Holy Roman emperor.

The Muslim conquest of Byzantine territory in Asia Minor has led to the rise of the Crusading movement.

Crusaders have captured the historic Christian city of Constantinople.

The Byzantines have regained their capital, Constantinople, and restored their empire.

The Black Death is ravaging Europe at this time. It will kill at least one third of the population.

The Ottoman sultanate is now penetrating deep into southwest Europe.

The Hundred Years War is ending in the expulsion of English forces from France.