What was the significance of the Edict of Milan, announcing tolerance of Christianity, and then the adoption of Christianity as Rome’s official religion? It meant that wherever the Roman Empire expanded, Christianity would go there also.
It ensured that all future emperors would be appointed by the Christian church.
It caused a holy war between pagan and Christian elements of the Roman Empire.
It required all members of Roman society to become practicing Christians.

In 911, a group of vikings lead by rollo besieged paris and chartres. after a victory near chartres on 26 august, charles decided to negotiate with rollo. the talks were led by hervé, the archbishop of reims. this resulted in the treaty of saint-clair-sur-epte, which granted rollo and his soldiers all the land between the river epte and the sea. it also granted him brittany, "for his livelihood". at the time, brittany was an independent land which france had not been able to conquer. in exchange, rollo promised the king his loyalty and military assistance when needed. also rollo also agreed to be baptised and to marry gisela, the king's daughter. the territory given rollo is about the same as upper normandy.