Well, as of all religion, it motivates people to do the right thing, "for god". So, religion builds confidence, morality, and much more into a society. As for the early New England Settlers, many did great things for their religions, like helping others, even dying for them. From a more scientific standpoint, I would say that religion helped and continues to help people motivate themselves to happier lifestyles.
The extent of the Byzantine territory was the highest during Justinian I rule. He almost reclaimed all territories that once belonged to the Roman Empire.
