How are refugees formed?

When natural disasters occur frequently, refugees are generally easy to form. In ancient times, if the victims could not get timely relief in case of flood or drought, they would become refugees. In order to survive, they will go begging elsewhere. When they encounter some injustice or deliberate provocation, they will easily form an ant crossing the border. Without food, local people can only beg with refugees without food, and it will get bigger and bigger. The main source is the macro-control of the country at that time, and the execution of officials is not good.