-how and why were the jews stripped of their citizenship and dehumanized in the early states of nazi persecution?

Many laws were introduced that didnt allow them to do as many things as other citizens were. For example, Jews were forced to wear big, bright, yellow stars on their shirts to denote their race/religion, they were given curfews, they were only allowed to purchase things from certain stores, and worse.

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).