A querist asked, “Why would you be confident that demon possession was minimal during the dark ages? I sure would not want to be a peon during that period, would you?”
The serfs in medieval Europe were better off than people in a lot of places. Being a serf in AD 500 was not a lot different from being a tenant farmer in AD 1910. Except for some technological advances, being a serf was not much worse than being a farm hand in 1959. The advantage our country has enjoyed was a long period of peace in this land. Maurauders and invading armies were the thing that caused the most trouble to the common people in Europe. The Saracens, Monguls, Germanic tribes, Hungarians, Visigoths, Huns, Vikings, and various other groups often went plundering during this period. It is hard to make a living when people come and destroy them. The thing that Europe had in common was a unified Church that ruled over the hearts of men.
The thousand year reign of Christ would imply that all powers were subject to Him whereever His rule was. I think the time from 345-1345 was the millennium and the place was in Europe. During that time, if Christ was reigning, then He would not have rebellious evil spirits running around loose. I am confident that demon possession was minimual because it was the time of His reign and because Zech 13 and I Cor 13 both require that the evil spirits pass out of the land.